White glass ceramic articles with opacity and high fracture toughness and methods of making same

Abstract

The invention relates to a glass ceramic article comprising (in mol%): 67-74% SiO2; 2 to 6% of Al2O3; 0.5% to 1.5% of P2O5; 18% to 25% of Li2O; 0 to 1% of Na2O; 0 to 1% of K2O; 1 to 4% of ZrO2; 0-2% of CaO; and from 0.001% to 0.5% of SnO2. The glass ceramic article is opaque and further comprises a lithium disilicate crystalline phase, a beta-spodumene solid solution crystalline phase, a Zr-based crystalline phase, and a lithium phosphate crystalline phase. The glass ceramic article may further have a fracture toughness (Kic) of from 1.0 to 3.0 MPa * m < 1 / 2 >, as measured by the Chevron Notch Shart Bar Method, and an opacity of from 60 to 97%, as measured by a glass ceramic article having a thickness of 0.5 mm.

Description

[0001] Cross - reference to related applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 428,773, filed on November 30, 2022, the content of which is hereby incorporated by reference in its entirety and for all purposes. Technical field

[0003] This disclosure generally relates to glass - ceramic articles, and more particularly, to white glass - ceramic articles having opacity and high fracture toughness, including such glass - ceramic articles formed from precursor glass compositions, for use in a variety of applications, including but not limited to mobile devices, cooktop panels, and cooking utensils. Background art

[0004] Glass - ceramic materials have been widely used in various applications. Glass - ceramic cooktop panels and cooking utensils are widely used in modern kitchens. Recently, white opaque glass - ceramics in the field of Li2O - Al2O3 - SiO2 (“LAS”) compositions have also been developed as an attractive component for mobile devices due to a combination of properties: white color, opacity, radio - wave transparency, and suitability for chemical strengthening by ion - exchange.

[0005] However, improving the mechanical properties of glass - ceramic materials, particularly damage resistance and fracture toughness, remains an ongoing challenge in the materials community. In the case of glass - ceramics (such as those for mobile device applications), the development of these mechanical properties has mainly revolved around glass - ceramic compositions that exhibit transparency and / or translucency suitable for covering display components.

[0006] Accordingly, there is still a need for glass - ceramic articles having opacity and high fracture toughness, and more particularly, white glass - ceramic articles, as well as methods for manufacturing such articles. Summary of the invention

[0007] According to one aspect of the present disclosure, there is provided a glass - ceramic article comprising (in mol%):

[0008] 68 - 70% SiO2;

[0009] 3.5 - 4.5% Al2O3;

[0010] 0.5 - 1.5% P2O5;

[0011] 20 - 24% Li2O;

[0012] 0 - 0.5% Na2O;

[0013] 0 - 0.5% K2O;

[0014] 2.5 - 3.1% ZrO2;

[0015] 0.5 - 1.0% CaO;

[0016] 0 - 0.2% Fe2O3;

[0017] 0 - 0.2% HfO2; and

[0018] 0.001 - 0.2% SnO2. The glass - ceramic article is opaque and further comprises a lithium disilicate crystalline phase, a β - spodumene solid - solution crystalline phase, a Zr - based crystalline phase, and a lithium phosphate crystalline phase.

[0019] According to another aspect of the present disclosure, there is provided a glass - ceramic article comprising (in mol%):

[0020] 70 - 72% SiO2;

[0021] 3.5 - 4.5% Al2O3;

[0022] 0.5 - 1.5% P2O5;

[0023] 20 - 24% Li2O;

[0024] 0 - 0.5% Na2O;

[0025] 0 - 0.5% K2O;

[0026] 1.7 - 2.3% ZrO2;

[0027] 0 - 0.5% CaO;

[0028] 0 - 0.2% Fe2O3;

[0029] 0 - 0.2% HfO2; and

[0030] 0.001 - 0.2% SnO2. The glass - ceramic article is opaque and comprises a β - spodumene solid - solution crystalline phase, a lithium disilicate crystalline phase, and one or more ZrO2 - containing crystalline phases. Further, the glass - ceramic article is derived from a glass precursor having a β - OH content of 0.1 / mm to 0.5 / mm.

[0031] According to other aspects of the present disclosure, there is provided a glass - ceramic article comprising (in mol%):

[0032] 67 - 74% SiO2;

[0033] 2 - 6% Al2O3;

[0034] 0.5 - 1.5% P2O5;

[0035] 18 - 25% Li2O;

[0036] 0 - 1% Na2O;

[0037] 0 - 1% K2O;

[0038] 1 - 4% ZrO2;

[0039] 0 - 2% CaO; and

[0040] 0.001 - 0.5% SnO2. The glass - ceramic article is opaque and further comprises a lithium disilicate crystalline phase, a β - spodumene solid - solution crystalline phase, a Zr - based crystalline phase, and a lithium phosphate crystalline phase. The glass - ceramic article may further have a fracture toughness (K 1 / 2 ) of 1.0 to 3.0 MPa×m IC as measured by the Chevron Notch Short Bar Method, and an opacity of about 60 to 97% as measured by a glass - ceramic article having a thickness of about 0.5 mm.

[0041] Additional features and advantages will be set forth in the detailed description which follows and, in part, will be obvious from the description, or may be learned by practice of the embodiments described herein, which embodiments include the detailed description which follows, the claims, as well as the drawings.

[0042] It should be understood that the foregoing general description and the following detailed description are exemplary and intended to provide an overview or framework for understanding the nature and characteristics of the claims. The drawings are included to provide a further understanding and are incorporated into and constitute a part of this specification. The drawings illustrate one or more embodiments and, together with the description, serve to explain the principles and operations of the various embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 According to one or more embodiments of the present disclosure, a glass - ceramic article having a compressive stress zone is schematically depicted;

[0044] Figure 2A is a plan view of a mobile device incorporating any glass - ceramic article, according to one or more embodiments of the present disclosure;

[0045] Figure 2B is Figure 2A a perspective view of the mobile device;

[0046] Figure 3is the X-ray diffraction (XRD) spectrum of a glass-ceramic article according to one or more embodiments of the present disclosure;

[0047] Figure 4A is a box plot of the Knoop hardness levels of three groups of glass-ceramic articles having different compositions and subjected to different ceramization conditions, according to an embodiment of the present disclosure;

[0048] Figure 4B and 4C are, respectively, microprobe distributions of the Na2O and K2O concentrations as a function of depth in a glass-ceramic article that has been subjected to an ion-exchange treatment, according to an embodiment of the present disclosure; Figure 4A

[0049] Figure 5A and 5B are scanning electron microscope (SEM) images of a glass-ceramic article according to one or more embodiments of the present disclosure;

[0050] Figure 5C and 5D are, according to an embodiment of the present disclosure, Figure 5A and 5B SEM images of glass-ceramic articles and glass-ceramic articles having different compositions and subjected to different ceramization conditions;

[0051] Figure 6A is a plot of the transmittance versus the wavenumber in the near-infrared (NIR) spectrum of glass compositions having different β-OH contents, which can be ceramized to obtain glass-ceramic articles according to an embodiment of the present disclosure;

[0052] Figure 6B is, according to an embodiment of the present disclosure, Figure 6A differential scanning calorimetry (DSC) plots of two glass compositions;

[0053] Figure 7A is a plot of the opacity versus the amount of zirconia in three glass-ceramic articles, according to an embodiment of the present disclosure;

[0054] Figure 7B is a plot of the amount of secondary phase as a function of time in two glass-ceramic articles during the growth stage of a ceramization cycle at 875 °C, according to an embodiment of the present disclosure;

[0055] Figure 8A is the XRD spectrum of a glass-ceramic article according to an embodiment of the present disclosure;

[0056] Figure 8B is Figure 8A the XRD spectrum of, with 2θ from 25° to 35° magnified; and ​

[0057] Figure 9 According to an embodiment of the present disclosure, it is a graph showing the amount of zirconia in two glass-ceramic products varying with the nucleation temperature. Detailed implementation manners

[0058] In the following detailed description, for purposes of explanation and not limitation, example embodiments that disclose specific details are set forth to provide a thorough understanding of the various principles of the present disclosure. However, it will be apparent to those of ordinary skill in the art who benefit from the present disclosure that the present disclosure may be practiced in other embodiments without the specific details disclosed herein. In addition, descriptions of well-known devices, methods, and materials may be omitted so as not to obscure the description of the various principles of the present disclosure. Finally, where applicable, the same reference numerals refer to the same elements.

[0059] As used herein, a range may be expressed as from “about” a particular value and / or to “about” another particular value. When expressing such a range, another embodiment includes from a particular value and / or to another particular value. In addition, when the term “about” is used to denote one or both endpoints of a range or any particular value, each such endpoint or value modified by “about” may vary within ±5% of the stated endpoint or value. Similarly, when a value is expressed as an approximation by use of the antecedent “about”, it is to be understood that the particular value forms another embodiment. It should be further understood that each endpoint of a range is significant relative to the other endpoint and independent of the other endpoint.

[0060] As used herein, directional terms such as “upper”, “lower”, “right”, “left”, “front”, “rear”, “top”, “bottom” are made only with reference to the drawings drawn and are not intended to imply absolute orientation.

[0061] Unless otherwise expressly stated, no method set forth herein is intended to be construed as requiring that its steps be performed in a particular order. Accordingly, where method claim steps are not actually recited in the order they are to be performed or where it is not otherwise specifically stated in the claims or the description that the steps are limited to a particular order, no inference of order is to be made in any respect. This applies to any possible non-explicit basis for interpretation, including: logical issues relative to step arrangement or operational flow; plain meaning derived from grammatical organization or punctuation; and the number or type of embodiments described in the specification.

[0062] As used herein, unless the context clearly indicates otherwise, the singular forms “a”, “an” and “the” include plural referents. Thus, for example, unless the context clearly states otherwise, reference to “a component” includes aspects having two or more such components.

[0063] As described herein, X-ray diffraction (XRD) spectra were measured using a D4 Endeavor X-ray diffraction system equipped with Cu radiation and a LynxEye XE-T detector manufactured by Bruker Corporation (Billerica, MA), and were evaluated using Rietveld analysis techniques understood by those skilled in the art of the present disclosure to develop and characterize the phase combinations present.

[0064] Also as described herein, scanning electron microscope (SEM) images were generated by a Zeiss GeminiSEM 500 scanning electron microscope, where specific parameters were used to generate the images identified in the figures of the present disclosure.

[0065] As described herein, differential scanning calorimetry (DSC) was performed according to techniques understood by those of ordinary skill in the art of the present disclosure. Unless otherwise indicated, samples of the present disclosure were subjected to DSC and heated to 1000 °C at 10 °C / min in a platinum pan under an argon atmosphere and analyzed in a Netzsch 404F1 high-resolution DSC device.

[0066] As used herein, the "Knoop hardness" of the glass-ceramic articles of the present disclosure was measured with a Mitutoyo HM114-320243 at a 200-g load and reported in kgf / mm 2 units.

[0067] As described herein, the "elastic modulus" (also referred to as the "Young's modulus") of the glass-ceramic articles is provided in gigapascals (GPa) and was measured by resonant ultrasound spectroscopy according to ASTM E2001-13. The shear modulus (also provided in GPa) and Poisson's ratio of the glass-ceramic articles of the present disclosure were also measured by resonant ultrasound spectroscopy according to ASTM E2001-13.

[0068] As used herein, the term "fracture toughness" refers to the K IC value and was measured using the V-notch short rod test method described in ASTM E 1304-97, the contents of which are incorporated herein by reference in their entirety. Unless otherwise indicated, fracture toughness values were measured on articles that were not strengthened (e.g., by ion exchange strengthening treatment).

[0069] As used herein, the "compressive stress zone" is a region in an embodiment of the glass-ceramic articles of the present disclosure where alkali metal ions (e.g., K + ions) have been exchanged for ion-exchangeable alkali metal ions (Na +ions), which is carried out after melting and before or after the ceramization process. Additionally, the terms "compression depth" and "DOC" refer to the location in the glass-ceramic article where the compressive stress transitions to tensile stress. Further, the terms "depth of layer" and "DOL" refer to the depth within the glass-ceramic article that defines the depth of alkali metal ion exchange after undergoing the ion-exchange strengthening process. Unless otherwise specified, the DOL used herein refers to the depth of potassium ion exchange in the glass-ceramic article.

[0070] As used herein, the term "transmittance" or "average transmittance" is defined as the percentage of the incident light power that is transmitted through a material (e.g., a cover article, a substrate, an outer layer film, or a portion thereof) within a given wavelength range. The term "reflectance" is similarly defined as the percentage of the incident light power that is reflected from a material (e.g., a cover article, a substrate, or an outer layer film, or a portion thereof) within a given wavelength range. Transmittance and reflectance are measured using a specific line width. As used herein, "average transmittance" refers to the average amount of the incident light power that is transmitted through a material within a defined wavelength region (e.g., the "optical wavelength region", which is also defined herein as 400 nm to 800 nm). Unless otherwise specified, a suitable interval for average transmittance measurement is 5 nm. As used herein, "average reflectance" refers to the average amount of the incident light power that is reflected by a material.

[0071] When used to describe a glass-ceramic article formed from a precursor glass composition as described herein, the term "opaque" means that the glass-ceramic article has an average transmittance of less than 20% when measured at a normal incidence for light in the wavelength range of 400 nm - 800 nm (including the endpoints) at an article thickness of 0.8 mm.

[0072] As used herein, as understood by those skilled in the art to which this disclosure pertains, the "color" or "reflected color" associated with the glass-ceramic articles of this disclosure is measured as the reflected color given in the CIELAB color space (CIE L*, a*, and b* coordinate systems), which uses the CIE F02 - 10 illuminant, under SCI UVC conditions, with an aperture of 25 mm. Additionally, unless otherwise specified, a white background reference ("white tile") or a black background reference ("black well") is used for all measurements reported in this disclosure. Further, all opacity measurements reported in this disclosure are obtained using this same system and parameters.

[0073] As used herein, the term "failure height" means the lowest height at which a device including a glass-ceramic article fails (i.e., cracks) a glass-dominated article after a drop. A drop test method is used to determine the failure height of the device. The drop test method involves performing a front-drop test on a disc to which a glass-dominated article is attached. During the drop test described below, the glass-ceramic article is attached to the disc (e.g., with double-sided tape or with epoxy resin). The thickness of the glass-ceramic article to be tested is similar to or equal to the thickness that will be used in a given handheld consumer electronic device, such as 0.5 mm or 0.6 mm. The disc is a structure designed to mimic the size, shape, and weight distribution of a given device (e.g., a cellular phone). Hereinafter, the term "disc" means a structure having a weight of 126.0 grams, a length of 133.1 mm, a width of 68.2 mm, and a height of 9.4 mm. In an embodiment, the disc has dimensions and a weight similar to a handheld electronic device.

[0074] An exemplary device drop machine can be used to perform the drop test method. The device drop machine includes a chuck having chuck jaws. The disc is fixed in the chuck jaws, and the glass-ceramic article is attached to the chuck jaws and faces downward. The chuck is ready to drop from, for example, an electromagnetic chuck lifter. Subsequently, the chuck is released, and during its fall, the chuck jaws are triggered to open by, for example, a proximity sensor. When the chuck jaws open, the disc is released. At this time, the falling disc strikes a drop surface. The drop surface can be sandpaper, such as 180 grit sandpaper, 80 grit sandpaper, 60 grit sandpaper, or 30 grit sandpaper, which is located on a steel plate. If the glass-dominated article attached to the disc withstands the drop (i.e., does not crack), the chuck is set at a higher height and the test is repeated. Then, the failure height is the lowest height at which the disc including the glass-ceramic article drops and fails the glass-ceramic article. At multiple heights, such as at 20 cm, 30 cm, 40 cm, 50 cm, 60 cm, 70 cm, 80 cm, 90 cm, 100 cm, 110 cm, 120 cm, 130 cm, 140 cm, 150 cm, 160 cm, 170 cm, and testing a single glass-ceramic article in 10 cm increments until the glass-ceramic article fails due to breakage. Replace the sandpaper after the glass-ceramic article fails.

[0075] As used herein, the term "retained strength" or "retained strength test method" refers to the strength of a glass-ceramic article after damage is induced by an impact force when the article is bent to impart a tensile stress. Damage is induced according to the method described in U.S. Patent Publication No. 2019 / 0072469A1, which is incorporated herein by reference. For example, an apparatus for impact testing a glass-ceramic article can include a pendulum that includes a plumb bob attached to a pivot. As used herein, the term "plumb bob" on the pendulum is a heavy weight that is suspended from the pivot by an arm and connected to the pivot. Thus, the plumb bob is connected to the pivot by the arm. The plumb bob includes a base for receiving the glass-ceramic article, and the glass-ceramic article is secured to the base. The apparatus further includes an impact object positioned such that when the pendulum is released from a position at an angle greater than zero from the equilibrium position, the surface of the pendulum contacts the impact object.

[0076] According to the retained strength test method, the impact object includes an abrasive sheet having an abrasive surface that contacts the outer surface of the glass-ceramic article. The abrasive sheet can comprise sandpaper, which can have an abrasive grit size in the range of 30 grit to 1000 grit or 100 grit to 300 grit, such as 80 grit, 120 grit, 180 grit, and 1000 grit sandpaper. Unless otherwise specified, 180 grit, 80 grit, or 30 grit sandpaper is used herein to measure retained strength. Additionally, for the purposes of the present disclosure, the impact object is in the form of a 6 mm diameter sandpaper disk fixed to the apparatus. A glass-ceramic article having a thickness of approximately 600.0 μm is secured to the plumb bob. A new sandpaper disk is used for each impact. The glass-ceramic article is damaged at an impact force of approximately 500.0 N by pulling the swing of the apparatus arm to an angle of approximately 90°. Approximately 10 samples of each glass-ceramic article are impacted.

[0077] Twenty-four hours after damage is induced, a four-point bend (4PB) fracture test is performed on the glass-ceramic article according to the retained strength test method. The damaged glass-ceramic article is placed on support bars (support span) with the damage location between the bottom (i.e., on the tension side) and the loading path (loading span). For the purposes of the present disclosure, the loading span is 18 mm and the support span is 36 mm. The radius of curvature of the loading bar and the support bars is 3.2 mm. A screw-driven testing machine ( Norwood, Massachusetts, USA) is used to apply loading at a constant displacement rate of 5 mm / min until the glass fails. The 4PB test is performed at a temperature of 22 °C ± 2 °C and a relative humidity (RH) of 50% + 5%. The fracture stress (or applied failure stress) σ app applied in the four-point bend (4PB) is calculated as follows by Equation (1):

[0078]

[0079] Wherein, P is the maximum failure load, L (= 36 mm) is the distance between the support bars (support span), a (= 18 mm) is the distance between the loading bars (loading span), b is the width of the glass plate, h is the thickness of the glass plate, and v is the Poisson's ratio of the glass composition. The term (1 / (1 - v 2 )) in Equation (1) accounts for the strengthening effect of the plate. In four-point bending, the stress is constant under the loading span, and thus, the damaged site is under mode I uniaxial tensile stress loading. The stress rate of the four-point bending test of the sample is estimated to be 15 to 17 MPa / sec. The retained strength of the glass-ceramic composition is the highest applied fracture stress at which no failure occurs (e.g., 300 MPa, 350 MPa, 400 MPa, 425 MPa, etc.).

[0080] As used herein, the term "precursor glass composition" refers to a glass composition that can form a glass-ceramic article after heat treatment.

[0081] As used herein, the term "glass-ceramic article" refers to an article formed by heat treating a glass article formed from a precursor glass composition to induce nucleation of a crystalline phase, such that the glass-ceramic article includes a crystalline phase and a residual glass phase.

[0082] As used herein, the term "crystalline phase size" refers to the size of the maximum dimension of the crystalline phase determined by examining and evaluating SEM micrographs.

[0083] Generally speaking, the present disclosure relates to glass-ceramic articles having opacity and high fracture toughness and methods for manufacturing such articles. The precursor glass compositions (i.e., precursor glasses) and glass-ceramic articles described herein can generally be described as lithium aluminosilicate glasses or glass-ceramics and contain SiO2, Al2O3, and Li2O. In addition to SiO2, Al2O3, and Li2O, the glasses and glass-ceramics practiced herein can also contain alkaline oxides such as Na2O, K2O, Rb2O, or Cs2O, as well as P2O5 and ZrO2, and many other components as described below. In one or more embodiments, the main crystalline phases include lithium silicate, β-spodumene solid solution, lithium phosphate, and a Zr-based crystalline phase. Other crystalline phases that may be present include β-quartz solid solution, cristobalite, and rutile, depending on the composition of the precursor glass.

[0084] More specifically, the present disclosure relates to a group of Li2O-Al2O3-SiO2 glass-ceramic articles having lithium disilicate and β-spodumene solid solution as the main crystalline phases, and ZrO2, β-quartz, cristobalite, lithium phosphate, sogdianite, and / or zircon as the minor phases. Generally, the composition may contain 55-75% SiO2, 0.2-10% Al2O3, 0-5% B2O3, 15-30% Li2O, 0-2% Na2O, 0-2% K2O, 0-2% CaO, 0-2% MgO, 0-2% ZnO, 0.2-3.0% P2O5, 0.1-10% ZrO2, 0-4% TiO2, 0.001-1.0% SnO2, and 0-2% Y2O3 in mole percentages. The two crystalline phases (including β-spodumene solid solution and lithium disilicate) and the residual glass phase in the glass-ceramic articles of the present disclosure can be ion-exchanged in a NaNO3 (and / or KNO3, or AgNO3) bath to form a compressive layer (i.e., "surface compressive stress") on the surface, thereby producing improved mechanical properties. In some embodiments, the glass-ceramic articles of the present disclosure constitute a family of white glass-ceramics in the Li2O-Al2O3-SiO2 (LAS) system, which contain lithium silicate and β-spodumene solid solution as the main crystalline phases, and lithium phosphate, zirconia, and zirconia-silicate as the key minor phases.

[0085] As described above, the glass-ceramic articles of the present disclosure can exhibit opacity and high fracture toughness. Regarding opacity, as measured by an article with a thickness of about 0.5 mm, embodiments of the glass-ceramic articles can exhibit an opacity of 60-97%. Regarding fracture toughness, as measured by the V-notch short rod method, embodiments of the glass-ceramic articles can exhibit a fracture toughness (K 1 / 2 ) of 1.0 to 3.0 MPa×m IC . Embodiments of the glass-ceramic articles of the present disclosure can also be formulated and / or processed with a glass precursor having a β-OH content of 0.15 / mm to 0.4 / mm (of the precursor article) to obtain various benefits, such as developing and / or enhancing the mechanical and / or optical properties of the resulting glass-ceramic articles.

[0086] Regarding the precursor glass composition of the present disclosure, SiO2 is the main glass former and can serve to stabilize the network structure of the precursor glass and the glass-ceramic article. In embodiments, the precursor glass or glass-ceramic composition comprises 55 to 80 mol% SiO2. In embodiments, the precursor glass or glass-ceramic composition comprises 60 to 80 mol% SiO2. In embodiments, the precursor glass or glass-ceramic composition comprises 65 to 75 mol% SiO2. In embodiments, the precursor glass or glass-ceramic composition comprises 67 to 74 mol% SiO2. In some embodiments, the glass or glass-ceramic composition can comprise 55 to 80 mol%, 55 to 77 mol%, 55 to 75 mol%, 55 to 73 mol%, 60 to 80 mol%, 60 to 77 mol%, 60 to 75 mol%, 60 to 73 mol%, 60 to 72 mol%, 64 to 80 mol%, 64 to 77 mol%, 64 to 75 mol%, 64 to 74 mol%, 64 to 73 mol%, 64 to 72 mol%, 67 to 80 mol%, 67 to 77 mol%, 67 to 75 mol%, 67 to 74 mol%, 67 to 73 mol%, 67 to 72 mol%, 68 to 70 mol%, 70 to 80 mol%, 70 to 77 mol%, 70 to 75 mol%, 70 to 72 mol%, 73 to 80 mol%, 73 to 77 mol%, 73 to 75 mol%, 75 to 80 mol%, 75 to 77 mol%, or 77 to 80 mol% SiO2, or any and all subranges formed by any of these endpoints.

[0087] Like SiO2, Al2O3 can also provide stability to the network and also provide improved mechanical properties and chemical durability. However, if the amount of Al2O3 is too high, the fraction of lithium disilicate crystals may decrease, possibly to the extent that an interlocking structure cannot be formed. The amount of Al2O3 can be adjusted to control the viscosity. Additionally, if the amount of Al2O3 is too high, the viscosity of the melt generally also increases. In embodiments, the glass or glass-ceramic composition can comprise 1 to 8 mol% Al2O3. In embodiments, the glass or glass-ceramic composition can comprise 1.5 to 7 mol% Al2O3. In embodiments, the glass or glass-ceramic composition can comprise 1.0 to 6 mol% Al2O3. In embodiments, the glass or glass-ceramic composition can comprise 1.0 to <7 mol% Al2O3. In some embodiments, the glass or glass-ceramic composition can comprise 1 to 6 mol%, 2 to 6 mol%, 3 to 6 mol%, 3.5 to 6 mol%, 3.5 to 5.5 mol%, 3.5 to 5 mol%, 3.5 to 4.5 mol% Al2O3, or any and all subranges formed by any of these endpoints.

[0088] In the precursor glasses and glass-ceramic articles described herein, Li2O contributes to the formation of a lithium disilicate crystalline phase. To obtain lithium disilicate as the primary crystalline phase, it is desirable to have at least 15 mol% Li2O in the composition. However, if the concentration of Li2O is too high (greater than 30 mol%), the composition becomes highly fluid and the delivery viscosity will be too low to form sheets. In some embodiments of the composition, the glass or glass-ceramic may comprise from 15 mol% to 30 mol% Li2O. In other embodiments, the glass or glass-ceramic may comprise from 18 mol% to 25 mol% Li2O. In other embodiments, the glass or glass-ceramic may comprise from 20 mol% to 24 mol% Li2O. In some embodiments, the glass or glass-ceramic composition may comprise from 15 to 30 mol%, from 15 to 28 mol%, from 15 to 26 mol%, from 15 to 24 mol%, from 15 to 22 mol%, from 18 to 30 mol%, from 18 to 28 mol%, from 18 to 26 mol%, from 18 to 25 mol%, from 18 to 24 mol%, from 18 to 22 mol%, from 19 to 30 mol%, from 19 to 28 mol%, from 19 to 26 mol%, from 19 to 24 mol%, from 19 to 22 mol%, from 20 to 30 mol%, from 20 to 28 mol%, from 20 to 26 mol%, from 20 to 24 mol%, from 20 to 22 mol% Li2O, or any and all subranges formed by any of these endpoints.

[0089] As described above, Li2O can generally be used to form the glass-ceramic articles of the embodiments, but other alkaline oxides (e.g., K2O and Na2O) tend to reduce glass-ceramic formation and form aluminosilicate residual glass in the glass-ceramic rather than the ceramic phase. Accordingly, the compositions described herein generally have a low amount of non-lithium alkaline oxides. In some embodiments, the glass or glass-ceramic composition may comprise from 0 to 4 mol% R2O, where R is one or more of the alkali metal cations Na and K. In some embodiments, the glass or glass-ceramic composition may comprise from 0 to 3 mol% R2O, where R is one or more of the alkali metal cations Na and K. In some embodiments, the glass or glass-ceramic composition may comprise from 0 to 3 mol%, from 0 to 2 mol%, from 0 to 1 mol%, from 0 to 0.5 mol%, >0 to 3 mol%, >0 to 2 mol%, >0 to 1 mol%, >0 to 0.75 mol%, >0 to 0.5 mol%, from 1 to 3 mol%, from 1 to 2 mol%, from 1.5 to 3 mol% and from 1.5 to 2 mol% Na2O, K2O, or combinations thereof. It should be understood that the R2O concentration may be within the subranges formed by any and all of the foregoing endpoints.

[0090] Optionally, the glass and glass-ceramic articles herein may contain boron, e.g., 0 to 5 mol%, or 0 to 2 mol% B2O3. In embodiments, the precursor glass composition or glass-ceramic article may contain 0 to 5 mol%, 0 to 4 mol%, 0 to 3 mol%, 0 to 2 mol%, 0 to 1 mol%, >0 to 5 mol%, >0 to 4 mol%, >0 to 3 mol%, >0 to 2 mol%, >0 to 1 mol%, 1 to 5 mol%, 1 to 4 mol%, 1 to 2 mol%, 2 to 5 mol%, 2 to 4 mol%, 3 to 5 mol%, 3 to 4 mol%, 4 to 5 mol%, or any and all subranges formed by any of these endpoints. In some embodiments, the precursor glass and glass-ceramic article is substantially free of B2O3. As used herein, the term "substantially free of" means that the component is not intentionally added to the material but may be present as an impurity, e.g., in an amount up to 0.01 mol%.

[0091] Precursor glass compositions and glass-ceramic articles can include P2O5. P2O5 can act as a nucleating agent to produce substantial nucleation of a crystalline phase from the glass and glass-ceramic compositions. If the concentration of P2O5 is too low, the precursor glass will indeed crystallize, but only at a higher temperature (due to lower viscosity); however, if the concentration of P2O5 is too high, devitrification during cooling during the formation of the precursor glass may be difficult to control. Embodiments can contain >0 to 3 mol% P2O5. Other embodiments can contain >0 to 2.5 mol% P2O5, >0 to 2 mol% P2O5, or even >0 to 1.5 mol% P2O5. The compositions of the embodiments can contain 0 to 3 mol%, 0 to 2.5 mol%, 0 to 2 mol%, 0 to 1.5 mol%, 0 to 1 mol%, >0 to 3 mol%, >0 to 2.5 mol%, >0 to 2 mol%, >0 to 1.5 mol%, >0 to 1 mol%, 0.2 to 3 mol%, 0.2 to 2.5 mol%, 0.2 to 2 mol%, 0.2 to 1.5 mol%, 0.2 to 1 mol%, 0.3 to 3 mol%, 0.3 to 2.5 mol%, 0.3 to 2 mol%, 0.3 to 1.5 mol%, 0.3 to 1 mol%, 0.4 to 3 mol%, 0.4 to 2.5 mol%, 0.4 to 2 mol%, 0.4 to 1.5 mol%, 0.4 to 1 mol%, 0.5 to 3 mol%, 0.5 to 2.5 mol%, 0.5 to 2 mol%, 0.5 to 1.5 mol%, 0.5 to 1 mol%, 0.7 to 3 mol%, 0.7 to 2.5 mol%, 0.7 to 2 mol%, 0.7 to 1.5 mol%, 0.7 to 1 mol%, 1 to 3 mol%, 1 to 2.5 mol%, 1 to 2 mol%, 1 to 1.5 mol%, 1.5 to 3 mol%, 1.5 to 2.5 mol%, 1.5 to 2 mol%, 2 to 3 mol%, 2 to 2.5 mol%, 2.5 to 3 mol% P2O5, or any and all subranges formed by any of these endpoints.

[0092] In the precursor glass compositions and glass-ceramic articles described herein, the addition of ZrO2 can improve the stability of Li2O-Al2O3-SiO2-P2O5 glasses by significantly reducing devitrification during formation and lowering the liquidus temperature. The addition of ZrO2 can form primary liquidus phases at high temperatures, thereby significantly reducing the liquidus viscosity. In some embodiments, the glass or glass-ceramic composition can comprise from 1 to 6 mol% ZrO2. In some embodiments, the glass or glass-ceramic composition can comprise from 2 to 5 mol% or from 1 to 4 mol% ZrO2. In some embodiments, the glass or glass-ceramic composition can comprise from 1 to 6 mol%, from 1 to 5 mol%, from 1 to 4 mol%, from 1.5 to 6 mol%, from 1.5 to 4 mol%, from 1.7 to 4 mol%, from 1.7 to 3 mol%, from 1.7 to 2.5 mol%, from 1.7 to 2.3 mol%, from 2 to 6 mol%, from 2 to 4 mol%, from 2.5 to 6 mol%, from 2.5 to 4 mol%, from 2.5 to 3.5 mol%, from 2.5 to 3.1 mol%, from 3 to 6 mol%, from 3 to 4 mol%, from 3.5 to 6 mol%, from 3.5 to 5 mol% ZrO2, or any subrange formed by these endpoints.

[0093] In one or more embodiments, the precursor glass compositions and glass-ceramic articles can comprise from 0 to 0.5 mol% SnO2 or another clarifying agent. In embodiments, the glass or glass-ceramic composition can comprise from 0 to 0.5 mol%, from 0 to 0.4 mol%, from 0 to 0.3 mol%, from 0 to 0.2 mol%, from 0 to 0.1 mol%, from 0.001 to 0.5 mol%, from 0.001 to 0.4 mol%, from 0.001 to 0.3 mol%, from 0.001 to 0.2 mol%, from 0.01 to 0.5 mol%, from 0.01 to 0.4 mol%, from 0.01 to 0.3 mol%, from 0.01 to 0.2 mol%, from 0.05 to 0.5 mol%, from 0.05 to 0.4 mol%, from 0.05 to 0.3 mol%, from 0.05 to 0.2 mol%, from 0.05 to 0.1 mol%, from 0.1 to 0.5 mol%, from 0.1 to 0.4 mol%, from 0.1 to 0.3 mol%, from 0.1 to 0.2 mol%, from 0.2 to 0.5 mol%, from 0.2 to 0.4 mol%, from 0.2 to 0.3 mol%, from 0.3 to 0.5 mol%, from 0.3 mol% to 0.4 mol%, or from 0.4 to 0.5 mol% SnO2, or any and all subranges formed by any of these endpoints.

[0094] CaO can enter the residual glass phase of the glass-ceramic articles of the present disclosure and / or participate in the crystallization of other minor phases in the glass-ceramic articles. In embodiments, the precursor glass and the glass-ceramic articles can contain 0 to 4 mol%, 0 to 3 mol%, or 0 to 2 mol% CaO. In some embodiments, the precursor glass or the glass-ceramic articles can contain 0 to 2 mol%, 0 to 1.75 mol%, 0 to 1.5 mol%, 0 to 1 mol%, 0 to 0.5 mol%, >0 to 2 mol%, >0 to 1.5 mol%, >0 to 1 mol%, >0 to 0.5 mol%, 0.5 to 2 mol%, 0.5 to 1.5 mol%, 0.5 to 1.0 mol% CaO, or any subrange formed by these endpoints.

[0095] In one or more embodiments, the precursor glass compositions and the glass-ceramic articles of the present disclosure can contain 0 to 0.5 mol% Fe2O3. In embodiments, the precursor glass composition or the glass-ceramic articles can contain 0 to 0.5 mol%, 0 to 0.4 mol%, 0 to 0.3 mol%, 0 to 0.2 mol%, 0 to 0.1 mol%, 0.05 to 0.5 mol%, 0.05 to 0.4 mol%, 0.05 to 0.3 mol%, 0.05 to 0.2 mol%, 0.05 to 0.1 mol%, 0.1 to 0.5 mol%, 0.1 to 0.4 mol%, 0.1 to 0.3 mol%, 0.1 to 0.2 mol%, 0.2 to 0.5 mol%, 0.2 to 0.4 mol%, 0.2 to 0.3 mol%, 0.3 to 0.5 mol%, 0.3 mol% to 0.4 mol%, 0.4 to 0.5 mol% Fe2O3, or any subrange formed by these endpoints.

[0096] In one or more embodiments, the precursor glass compositions and the glass-ceramic articles of the present disclosure can contain 0 to 0.5 mol% HfO2. In embodiments, the precursor glass composition or the glass-ceramic articles can contain 0 to 0.5 mol%, 0 to 0.4 mol%, 0 to 0.3 mol%, 0 to 0.2 mol%, 0 to 0.1 mol%, 0.05 to 0.5 mol%, 0.05 to 0.4 mol%, 0.05 to 0.3 mol%, 0.05 to 0.2 mol%, 0.05 to 0.1 mol%, 0.1 to 0.5 mol%, 0.1 to 0.4 mol%, 0.1 to 0.3 mol%, 0.1 to 0.2 mol%, 0.2 to 0.5 mol%, 0.2 to 0.4 mol%, 0.2 to 0.3 mol%, 0.3 to 0.5 mol%, 0.3 mol% to 0.4 mol% or 0.4 to 0.5 mol% HfO2, or any and all subranges formed by any of these endpoints.

[0097] Table 1 lists three compositional spaces (Examples A - C) of precursor glass compositions and glass - ceramic articles according to one or more embodiments shown and described herein.

[0098] Table 1 - Compositional Spaces of Glass Articles and Glass Precursors

[0099] Oxide mol% Example A Example B Example C <![CDATA[SiO2]]> 67-74％ 68-70％ 70-72％ <![CDATA[Al2O3]]> 2-6％ 3.5-4.5％ 3.5-4.5％ <![CDATA[P2O5]]> 0.5-1.5％ 0.5-1.5％ 0.5-1.5％ <![CDATA[Li2O]]> 18-25％ 20-24％ 20-24％ <![CDATA[Na2O]]> 0-1％ 0-0.5％ 0-0.5％ <![CDATA[K2O]]> 0-1％ 0-0.5％ 0-0.5％ <![CDATA[ZrO2]]> 1-4％ 2.5-3.1％ 1.7-2.3％ CaO 0-2％ 0.5-1.0％ 0-0.5％ <![CDATA[Fe2O3]]> ** 0-0.2％ 0-0.2％ <![CDATA[HfO2]]> ** 0-0.2％ 0-0.2％ <![CDATA[SnO2]]> 0.001-0.5％ 0.001-0.2％ 0.001-0.2％

[0100] Table 2 includes two exemplary compositions (Examples D1 and D2) of glass - precursor compositions and / or glass - ceramic articles according to one or more embodiments shown and described herein.

[0101] Table 2 - Exemplary Glass Articles and Glass - Precursor Compositions

[0102] Oxide mol% Example D1 Example D2 <![CDATA[SiO2]]> 70.8％ 69％ <![CDATA[Al2O3]]> 4.24％ 4.03％ <![CDATA[P2O5]]> 0.84％ 1.01％ <![CDATA[Li2O]]> 21.7％ 22.3％ <![CDATA[Na2O]]> 0.06％ 0.06％ <![CDATA[K2O]]> 0.07％ 0.07％ <![CDATA[ZrO2]]> 2.01％ 2.78％ CaO 0.03％ 0.71％ <![CDATA[Fe2O3]]> 0.02％ 0.02％ <![CDATA[HfO2]]> 0.02％ 0.03％ <![CDATA[SnO2]]> 0.15％ 0.01％

[0103] As previously mentioned, glass - ceramic articles derived from the glass - precursor compositions of the present disclosure may contain lithium disilicate. Lithium disilicate Li2Si2O5 is an orthorhombic crystal of corrugated sheets based on an array of Si2O5 tetrahedra. The crystal shape is typically flaky or platy, with distinct cleavage planes. The lithium - disilicate - based glass - ceramic articles of the present disclosure provide very desirable mechanical properties, including high bulk strength and fracture toughness, due to their microstructure of randomly oriented interlocking crystals. The glass - ceramic articles of the present disclosure can exhibit fracture toughness values of 1.0 to 3.0 MPa·m 1 / 2 in this compositional system.

[0104] Further strengthening of the lithium - disilicate glass - ceramic articles of the present disclosure can be achieved by ion - exchanging the smaller alkali - metal ions (e.g., Na + ions) in the article with larger alkali - metal ions (e.g., K + ions) present in a molten - salt bath. The resulting alkali - metal ion distribution (e.g., K + ions) and the accompanying compressive - stress distribution can be described by an error (erfcs) function after a short immersion time and by a parabolic (or quasi - parabolic) function after a longer immersion time in the salt bath.

[0105] In an embodiment, the weight percentage of the lithium disilicate crystalline phase in the glass-ceramic article of the present disclosure can be in the range of 20 to 60 wt%, 20 to 55 wt%, 20 to 50 wt%, 20 to 45 wt%, 20 to 40 wt%, 20 to 35 wt%, 20 to 30 wt%, 20 to 25 wt%, 25 to 60 wt%, 25 to 55 wt%, 25 to 50 wt%, 25 to 45 wt%, 25 to 40 wt%, 25 to 35 wt%, 25 to 30 wt%, 30 to 60 wt%, 30 to 55 wt%, 30 to 50 wt%, 30 to 45 wt%, 30 to 40 wt%, 30 to 35 wt%, 35 to 60 wt%, 35 to 55 wt%, 35 to 50 wt%, 35 to 45 wt%, 35 to 40 wt%, 40 to 60 wt%, 40 to 55 wt%, 40 to 50 wt%, 40 to 45 wt%, 45 to 60 wt%, 45 to 55 wt%, 45 to 50 wt%, 50 to 60 wt%, 50 to 55 wt%, or 55 to 60 wt%, or any and all subranges formed by any of these endpoints.

[0106] As previously described, the glass-ceramic article derived from the glass precursor composition of the present disclosure can contain a β-spodumene solid solution. The β-spodumene solid solution, also known as filled hydrothermal quartz (keatite), has a framework structure of corner-linked SiO4 and AlO4 tetrahedra that form interlocking rings, which in turn produce channels containing Li ions. The glass-ceramic article of the present disclosure based on the β-spodumene phase can be chemically strengthened in a salt bath, during which Na + (and / or K + ) replaces Li in the β-spodumene structure + , which causes surface compression and strengthening.

[0107] As previously described, the glass-ceramic article derived from the glass precursor composition of the present disclosure can contain one or more Zr-based crystalline phases. Monoclinic ZrO2 (baddeleyite) is an important geological mineral and has been extensively studied to understand its monoclinic-tetragonal-cubic phase transition and its relationship with the stabilization of tetragonal ZrO2 ceramics. Structure ceramics based on stabilized tetragonal ZrO2 exhibit excellent mechanical properties, which are attributed to the combination of multiple toughening mechanisms. Due to the high strength and toughness generated by the phase transition of ZrO2 from tetragonal to monoclinic, it is widely used as an advanced functional or structural ceramic in the dental, electronic, and abrasive industries. In addition, the high refractive index of ZrO2 (n = 2.16) makes it an excellent white refractive coating material in the glass-ceramic article of the present disclosure.

[0108] In some embodiments, the weight percentage of one or more ZrO2-containing crystalline phases in the glass-based articles of the present disclosure can be in the range of 0.5 to 4.0 wt%, 0.5 to 3.5 wt%, 0.5 to 3.0 wt%, 0.5 to 2.5 wt%, 0.5 to 2.0 wt%, 0.5 to 1.5 wt%, 0.5 to 1.0 wt%, 1.0 to 4.0 wt%, 1.0 to 3.5 wt%, 1.0 to 3.0 wt%, 1.0 to 2.5 wt%, 1.0 to 2.0 wt%, 1.0 to 1.5 wt%, or any and all sub-ranges formed by any of these endpoints.

[0109] In some embodiments, the glass-ceramic articles of the present disclosure have a residual glass content of 0 to 15 wt%, 0 to 10 wt%, 0 to 5 wt%, 1 to 10 wt%, 1 to 7.5 wt%, 1 to 5 wt%, 1 to 2.5 wt%, 1.5 to 7.5 wt%, 1.5 to 5 wt%, 1.5 to 4 wt%, 1.5 to 3 wt%, 2 to 5 wt%, 2 to 4 wt%, or 2 to 3 wt%, as determined by Rietveld analysis of the XRD spectrum. It should be understood that the residual glass content can be within the subranges formed by any and all of the aforementioned endpoints.

[0110] The present invention relates to the production of opaque white spodumene / lithium disilicate / ZrO2 glass-ceramics. Such glass-ceramics have high strength and high fracture toughness and are composed of interlocked lithium silicate crystals and β-spodumene particles of size >150nm in a glass matrix, thus having high fracture toughness and high bulk strength. The presence of a high refractive index phase (such as ZrO2) makes such glass-ceramics appear opaque white. In addition, the presence of an ion-exchangeable phase (β-spodumene) enables the formation of a surface compression layer, thereby improving the mechanical properties.

[0111] The color and opacity of the glass-ceramic article of the present disclosure can depend to a great extent on the ZrO that can be separated out in the material during the ceramming process (ceramming process) (also interchangeably referred to as "ceramming process (ceram process)" in this article) The amount of crystal. The property and amount of the different crystalline phases that can be separated out are usually subject to the control of the combined influence of the glass composition and the thermal treatment (ceramization) that is applied to the precursor glass composition to produce the glass-ceramic article. As previously mentioned, the ZrO in these glass-ceramic articles The amount of crystallization can be subject to Na in the precursor glass composition O and K The impact of O concentration, for a given ceramizing cycle, the higher the concentration of these elements, the ZrO that is separated out The amount of crystallization is lower.

[0112] In addition, according to some embodiments, for a given precursor glass composition having a given ceramization cycle, the amount of ZrO2 crystals in the resulting glass-ceramic article can be controlled by controlling or otherwise understanding the amount of dissolved water (β-OH content) in the glass. Without being bound by theory, the water content in the precursor glass composition can be understood or otherwise controlled while also adjusting the ceramization cycle to obtain a large amount of ZrO2 crystalline phase, which results in a higher opacity of the resulting glass-ceramic article. According to some embodiments, the melting process can be controlled to obtain a precursor glass having different dissolved water (β-OH) contents, thereby promoting and maximizing the crystallinity of the ZrO2 crystalline phase in the glass-ceramic article and employing a given ceramization formulation.

[0113] According to an embodiment of the glass-ceramic article of the present disclosure, the article has a phase combination composed of the following crystals: β-spodumene solid solution crystals with a size range between 0.5 and 2 μm, lithium disilicate needles with a length of 0.5 to 2 μm and a width of 100 to 500 nm, and uniformly dispersed zircon-dominated crystals (zirconia, zircon, and / or K2Zr2O5) with a size range between 50 and 500 nm, lithium phosphate crystals with a size range between 50 and 500 nm, wherein nosean is present as a minor phase (0 wt% to <2 wt%). Without being bound by theory, it is believed that the larger lithium disilicate particles and the dispersed ZrO2 phase distributed at the grain boundaries of the β-spodumene solid solution contribute to the higher fracture toughness of the glass-ceramic article of the present disclosure.

[0114] According to embodiments of the glass precursor composition and the glass-ceramic article of the present disclosure, the glass precursor composition can be adjusted or otherwise selected to have a β-OH content of 0.1 / mm to 0.5 / mm or 0.15 to 0.4 / mm. In an embodiment, the glass-ceramic article can be derived from a precursor glass composition that includes 0.5 / mm, 0.45 / mm, 0.40 / mm, 0.35 / mm, 0.30 / mm, 0.22 / mm, 0.25 / mm, 0.20 / mm, 0.17 / mm, 0.16 / mm, 0.15 / mm, 0.1 / mm, or any and all subranges formed between any of these values or endpoints.

[0115] According to one or more embodiments, the glass-ceramic article of the present disclosure may exhibit an opacity of about 60 - 97%, about 65 - 97%, or about 75 - 95%, as measured through an article having a thickness of about 0.5 mm. In embodiments, the glass-ceramic article exhibits an opacity of: about 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 89%, 88%, 87%, 86%, 85%, 84%, 83%, 82%, 81%, 80%, 79%, 78%, 77%, 76%, 75%, 74%, 73%, 72%, 71%, 70%, 69%, 68%, 67%, 66%, 65%, 64%, 63%, 62%, 61%, 60%, or any and all subranges formed between any of these values or endpoints. Additionally, in some embodiments, the glass-ceramic article formed from the precursor glass compositions described herein is opaque. That is, these glass-ceramic articles have an average transmittance of less than 20% when measured at a normal incidence for light in the wavelength range of 400 nm to 800 nm (including the endpoints) through an article having a thickness of 0.8 mm.

[0116] According to one or more embodiments, the color of the glass-ceramic article of the present disclosure is white or substantially white. Embodiments of the glass-ceramic article of the present disclosure may exhibit a reflected color given by L* of 80 to 98, a* of -3.0 to +3.0, and b* of -10.0 to +5.0 in the CIE color coordinate system. In some embodiments, the glass-ceramic article of the present disclosure exhibits a reflected color given by L* of 80 to 98, a* of -2.0 to 0, and b* of -8.0 to 0 in the CIE color coordinate system. According to another embodiment, the glass-ceramic article of the present disclosure exhibits a reflected color given by L* of 85 to 98, a* of -3.0 to +3.0, and b* of -5.0 to +5.0 in the CIE color coordinate system.

[0117] According to one or more embodiments, the glass-ceramic article of the present disclosure exhibits a fracture toughness (K 1 / 2 ) of 1.0 to 3.0 MPa×m IC , as measured using the V-notch short-rod test method described in ASTM E 1304 - 97. In some embodiments, the glass-ceramic article of the present disclosure exhibits a fracture toughness (K 1 / 2 ) of 1.5 to 3.0 MPa×m IC , as measured using the V-notch short-rod test method described in ASTM E1304 - 97. In embodiments, the glass-ceramic article exhibits a fracture toughness (K 1 / 2 ) of 3.0, 2.8, 2.6, 2.4, 2.2, 2.0, 1.8, 1.6, 1.4, 1.2, 1.0 MPa×m IC), or any and all sub-ranges formed between any of these values or endpoints.

[0118] According to one or more embodiments, the glass-ceramic articles (non-ion-exchanged strengthened articles) of the present disclosure exhibit a Knoop hardness greater than 500, 550, or even 600 kgf / mm 2 In some embodiments, the glass-ceramic articles of the present disclosure exhibit a Knoop hardness of 500, 525, 550, 575, 600, 625, 650, 675, 700 kgf / mm 2 ), or any and all sub-ranges formed between any of these values or endpoints.

[0119] According to some embodiments, the glass-ceramic articles of the present disclosure exhibit a modulus of elasticity greater than 85 GPa, 90 GPa, or even 95 GPa, as measured according to ASTM C623. In some embodiments, the glass-ceramic articles of the present disclosure exhibit a modulus of elasticity of 85 GPa, 87.5 GPa, 90 GPa, 92.5 GPa, 95 GPa, 97.5 GPa, or any and all sub-ranges formed between any of these values or endpoints.

[0120] According to some embodiments of the glass-ceramic articles of the present disclosure, when a sample is dropped from a height of at least 160 cm onto 80 grit sandpaper and / or from a height of at least 110 cm onto 60 grit sandpaper, the article can exhibit exemplary mechanical properties, i.e., no failure in the drop test method. In some embodiments, according to the drop test method, the glass-ceramic articles of the present disclosure can withstand a drop height of 160 cm, 170 cm, or even 180 cm onto 80 grit sandpaper. In some embodiments, according to the drop test method, the glass-ceramic articles of the present disclosure can withstand a drop height of 110 cm, 120 cm, or even 130 cm onto 60 grit sandpaper.

[0121] According to another embodiment of the glass-ceramic article of the present disclosure, when subjected to an ion-exchange process (see subsequent disclosure), according to the retained strength test method, these articles can exhibit an applied fracture stress of at least 400 MPa (by 4-point bending test) after being damaged by 180 grit sandpaper; an applied fracture stress of at least 350 MPa after being damaged by 80 grit sandpaper; and / or an applied fracture stress of at least 300 MPa after being damaged by 30 grit sandpaper. In some embodiments, according to the retained strength test method, after being damaged by 180 grit sandpaper, the glass-ceramic articles of the present disclosure can exhibit an applied fracture stress of at least 400 MPa, 450 MPa or even 500 MPa (by 4-point bending test). In some embodiments, according to the retained strength test method, after being damaged by 80 grit sandpaper, the glass-ceramic articles of the present disclosure can exhibit an applied fracture stress of at least 350 MPa, 400 MPa or even 450 MPa (by 4-point bending test). In some embodiments, according to the retained strength test method, after being damaged by 30 grit sandpaper, the glass-ceramic articles of the present disclosure can exhibit an applied fracture stress of at least 300 MPa, 350 MPa or even 400 MPa (by 4-point bending test).

[0122] The glass-ceramic article formed from the precursor glass composition described herein can be any suitable thickness, which can vary depending on the particular application in which the glass-ceramic article is used. In embodiments, the thickness of the glass-ceramic article can be greater than or equal to 250 μm and less than or equal to 6 mm, greater than or equal to 250 μm and less than or equal to 4 mm, greater than or equal to 250 μm and less than or equal to 2 mm, greater than or equal to 250 μm and less than or equal to 1 mm, greater than or equal to 250 μm and less than or equal to 750 μm, greater than or equal to 250 μm and less than or equal to 500 μm, greater than or equal to 500 μm and less than or equal to 6 mm, greater than or equal to 500 μm and less than or equal to 4 mm, greater than or equal to 500 μm and less than or equal to 2 mm, greater than or equal to 500 μm and less than or equal to 1 mm, greater than or equal to 500 μm and less than or equal to 750 μm, greater than or equal to 750 μm and less than or equal to 6 mm, greater than or equal to 750 μm and less than or equal to 4 mm, greater than or equal to 750 μm and less than or equal to 2 mm, greater than or equal to 750 μm and less than or equal to 1 mm, greater than or equal to 1 mm and less than or equal to 6 mm, greater than or equal to 1 mm and less than or equal to 4 mm, greater than or equal to 1 mm and less than or equal to 2 mm, greater than or equal to 2 mm and less than or equal to 6 mm, greater than or equal to 2 mm and less than or equal to 4 mm, or even greater than or equal to 4 mm and less than or equal to 6 mm, or any and all subranges formed by any of these endpoints.

[0123] In an embodiment, a method for manufacturing a glass-ceramic article includes heat treating a precursor glass composition (e.g., in an oven) at one or more preselected temperatures and for one or more preselected times to induce crystallization (i.e., nucleation and growth) of one or more crystalline phases (e.g., having one or more compositions, amounts, morphologies, sizes, or size distributions, etc.). In an embodiment, the heat treatment may include (i) heating the precursor glass composition to a nucleation temperature in an oven at a rate greater than or equal to 1°C / min and less than or equal to 10°C / min; (ii) maintaining the precursor glass composition at the nucleation temperature in an oven for a time greater than or equal to 0.25 hours and less than or equal to 5 hours to produce a nucleated crystallizable glass; (iii) heating the nucleated crystallizable glass to a crystallization temperature in an oven at a rate greater than or equal to 1°C / min and less than or equal to 10°C / min; (iv) maintaining the nucleated crystallizable glass at the crystallization temperature in an oven for a time greater than or equal to 0.25 hours and less than or equal to 5 hours to produce a glass-ceramic article; and (v) cooling the glass-ceramic article to room temperature. The heating rate disclosed herein refers to the rate of temperature change in the environment, such as the rate of temperature change in the oven. According to an embodiment, according to (ii), the precursor glass composition is maintained at the nucleation temperature for about 3 hours to 5 hours, such as 3 hours, 3.5 hours, 4.0 hours, 4.5 hours, 5.0 hours, and all durations between these values. According to an embodiment, according to (iv), the precursor glass composition is maintained at the crystallization temperature for about 3 hours to 5 hours, such as 3 hours, 3.5 hours, 4.0 hours, 4.5 hours, 5.0 hours, and all durations between these values.

[0124] In an embodiment, the nucleation temperature may be greater than or equal to 600°C and less than or equal to 900°C. In an embodiment, the nucleation temperature may be greater than or equal to 600°C or even greater than or equal to 650°C. In an embodiment, the nucleation temperature may be less than or equal to 900°C or even less than or equal to 800°C. In an embodiment, the nucleation temperature may be greater than or equal to 600°C and less than or equal to 900°C, greater than or equal to 600°C and less than or equal to 800°C, greater than or equal to 650°C and less than or equal to 900°C, or even greater than or equal to 650°C and less than or equal to 800°C, or any and all subranges formed by any of these endpoints. In some embodiments, the nucleation temperature for the precursor glass composition is 680°C, 700°C, 720°C, 740°C, 760°C, 780°C, 800°C, 820°C, and any nucleation temperature between these values. The nucleation temperature herein refers to the temperature of the environment in which nucleation occurs, such as the temperature of an oven.

[0125] In an embodiment, the crystallization temperature can be greater than or equal to 700 °C and less than or equal to 1000 °C. In an embodiment, the crystallization temperature can be greater than or equal to 700 °C or even greater than or equal to 750 °C. In an embodiment, the crystallization temperature can be less than or equal to 1000 °C or even less than or equal to 900 °C. In an embodiment, the crystallization temperature can be greater than or equal to 700 °C and less than or equal to 1000 °C, greater than or equal to 700 °C and less than or equal to 920 °C, greater than or equal to 750 °C and less than or equal to 1000 °C, or even greater than or equal to 750 °C and less than or equal to 920 °C, or any and all sub-ranges formed by any of these endpoints. In some embodiments, the crystallization temperature for the precursor glass composition is 825 °C, 850 °C, 875 °C, 890 °C, 900 °C, 920 °C, 925 °C, and any crystallization temperature between these values. The crystallization temperature herein refers to the temperature of the environment where crystallization occurs, such as the temperature of an oven.

[0126] Those skilled in the art will understand that the heating rate, nucleation temperature, and crystallization temperature described herein refer to the heating rate and temperature of the oven in which the precursor glass composition is heat-treated to produce the glass-ceramic article of the present disclosure.

[0127] In addition to the precursor glass composition, the temperature-time profile of the heat-treatment step of heating to the crystallization temperature and maintaining the temperature at the crystallization temperature is also reasonably specified to produce one or more of the following desired properties: the crystalline phase of the glass-ceramic article, the proportion of one or more major crystalline phases and / or one or more minor crystalline phases and the residual glass phase, the crystalline-phase combination of one or more major crystalline phases and / or one or more minor crystalline phases and the residual glass phase, and the grain size or grain-size distribution between one or more major crystalline phases and / or one or more minor crystalline phases, which in turn may affect the final integrity, quality, color, and / or opacity of the resulting glass-ceramic article.

[0128] As described above, embodiments of the glass precursor compositions and glass-ceramic articles of the present disclosure can be adjusted or otherwise selected to have a β-OH content of from 0.1 / mm to 0.5 / mm or from 0.15 to 0.4 / mm. Without being bound by theory, given the β-OH content present in the glass composition, the ceramization process for forming a glass-ceramic article from the precursor glass compositions of the present disclosure can be adjusted (e.g., by adjusting the nucleation temperature, nucleation duration, crystallization temperature, and / or crystallization duration) to maximize the crystallization of the ZrO2 crystalline phase and obtain a glass-ceramic article having a higher opacity and / or fracture toughness. Further, without being bound by theory, it is expected that for a given ceramization process condition, a higher amount of the ZrO2 crystalline phase and corresponding levels of opacity will be found in glass-ceramic articles derived from glass precursor compositions having a higher β-OH content. Additionally, it is expected that a higher amount of the ZrO2 crystalline phase and corresponding levels of opacity will be found in glass-ceramic articles derived from glass precursor compositions having the same β-OH content but subjected to a higher crystallization temperature and / or crystallization duration. That is, prior knowledge regarding the low β-OH content of the precursor glass composition can be used to optimize the ceramization process having a higher crystallization temperature and / or crystallization duration to produce a higher amount of the ZrO2 crystalline phase in the resulting glass-ceramic article, thereby contributing to a higher level of opacity.

[0129] The resulting glass-ceramic article can be provided as a sheet and then re-formed into a curved or bent sheet of uniform thickness by pressing, blowing, bending, sagging, vacuum forming, or other means. The re-forming can be carried out before the heat treatment, or the forming step can also be used as the heat treatment step, where the forming and heat treatment are carried out substantially simultaneously.

[0130] In embodiments, the glass-ceramic articles described herein are ion-exchangeable to facilitate strengthening of articles made from the precursor glass compositions of the present disclosure. In a typical ion-exchange process, smaller metal ions in the glass-ceramic article are replaced or "exchanged" by larger metal ions of the same valence in a layer near the outer surface of the glass-ceramic article made from the precursor glass composition. Replacing the smaller ions with the larger ions creates compressive stress within the layer of the glass-ceramic article made from the precursor glass composition. In embodiments, the metal ions are monovalent metal ions (e.g., Li + , Na + , K + , etc.), and the ion exchange is achieved by immersing the glass-ceramic article made from the precursor glass composition in a bath that contains at least one molten salt of the larger metal ion that is used to replace the smaller metal ions in the glass article. Alternatively, other monovalent ions such as Ag + , Tl + , Cu+ etc. can be exchanged for monovalent ions.

[0131] According to an embodiment, the glass-ceramic article of the present disclosure can be subjected to an ion-exchange process in a molten salt bath containing NaNO3 or KNO3 or a mixed molten salt bath. In the molten salt bath, lithium ions in the β-spodumene solid solution and the residual glass phase can be easily replaced by Na + or K + ions. During the ion-exchange process, the glass-ceramic article is held in the salt bath for a sufficient time for the exchange to occur on the surface and penetrate to a certain depth into the article. As a result of the ion exchange, a surface compression (CS) layer is generated by replacing Li and / or Na contained in the surface layer with Na or K having a larger ionic radius during chemical strengthening, such that the mechanical properties are increased in terms of the drop test method and / or the retention strength test method. One or more ion-exchange processes for strengthening a glass-ceramic article made from a precursor glass composition can include, but are not limited to, immersion in a single bath or multiple baths of the same or different compositions, with washing and / or annealing steps between immersions. According to an embodiment, the bath composition can contain 58 - 62 wt% KNO3 (e.g., 60 wt% KNO3), 38 - 42 wt% NaNO3 (e.g., 40 wt% NaNO3), and optionally a small amount of LiNO3 (e.g., 0.01 - 1 wt%, 0.12 wt%, etc.), and the bath temperature is set to 475 °C to 550 °C (e.g., 500 °C).

[0132] According to an embodiment, after exposure to the glass-ceramic article, the temperature of the ion-exchange solution (e.g., a molten salt bath of KNO3 and / or NaNO3) can be ≥350 °C and ≤550 °C, ≥350 °C and ≤500 °C, ≥360 °C and ≤450 °C, ≥370 °C and ≤440 °C, ≥360 °C and ≤420 °C, ≥370 °C and ≤400 °C, ≥375 °C and ≤475 °C, ≥400 °C and ≤500 °C, ≥410 °C and ≤490 °C, ≥420 °C and ≤480 °C, ≥430 °C and ≤470 °C, or even ≥440 °C and ≤460 °C, or any and all sub-ranges between the foregoing values. In an embodiment, the glass-ceramic article can be exposed to the ion-exchange solution for the following durations: ≥2 hours and ≤48 hours, ≥2 hours and ≤24 hours, ≥2 hours and ≤12 hours, ≥2 hours and ≤6 hours, ≥8 hours and ≤44 hours, ≥12 hours and ≤40 hours, ≥16 hours and ≤36 hours, ≥20 hours and ≤32 hours, or even ≥24 hours and ≤28 hours, or any and all sub-ranges between the foregoing values.

[0133] As described above, in an embodiment, the glass-ceramic article can be strengthened, for example, by ion exchange to produce a glass-ceramic article having damage resistance for applications (such as, but not limited to, glass for device housings). Refer toFigure 1 , the glass-ceramic article 100 has a first region under compressive stress that extends from the surface of the glass-ceramic substrate to the DOC (e.g., a region where smaller alkali metal ions (e.g., Na + ions) have been substantially exchanged by larger alkali metal ions (e.g., K + ions)) and a second region that extends from the DOC to the center or inner region of the glass (e.g., Figure 1 the central region 130 in). The first compressive layer 120 extends from the first surface 110 to a depth d1, and the second compressive layer 122 extends from the second surface 112 to a depth d2. These sections together define the compressive stress zone of the glass-ceramic article 100.

[0134] In an embodiment, the DOC of the glass-ceramic article can be in the range of ≥0.14t to ≤0.24t, where t is the thickness of the article, such as ≥0.15t to ≤0.24t, ≥0.16t to ≤0.24t, ≥0.17t to ≤0.24t, ≥0.18t to ≤0.24t, ≥0.19t to ≤0.24t, ≥0.20t to ≤0.24t, ≥0.21t to ≤0.24t, ≥0.22t to ≤0.24t, ≥0.23t to ≤0.24t, ≥0.14t to ≤0.23t, ≥0.15t to ≤0.23t, ≥0.16t to ≤0.23t, ≥0.17t to ≤0.23t, ≥0.18t to ≤0.23t, ≥0.19t to ≤0.23t, ≥0.20t to ≤0.23t, ≥0.21t to ≤0.23t, ≥0.22t to ≤0.23t, ≥0.14t to ≤0.22t, ≥0.15t to ≤0.22t, ≥0.16t to ≤0.22t, ≥0.17t to ≤0.22t, ≥0.18t to ≤0.22t, ≥0.19t to ≤0.22t, ≥0.20t to ≤0.22t, ≥0.21t to ≤0.22t, ≥0.14t to ≤0.21t, ≥0.15t to ≤0.21t, ≥0.16t to ≤0.21t, ≥0.17t to ≤0.21t, ≥0.18t to ≤0.21t, ≥0.19t to ≤0.21t, ≥0.20t to ≤0.21t, ≥0.14t to ≤0.20t, ≥0.15t to ≤0.20t, ≥0.16t to ≤0.20t, ≥0.17t to ≤0.20t, ≥0.18t to ≤0.20t, ≥0.19t to ≤0.20t, ≥0.14t to ≤0.19t, ≥0.15t to ≤0.19t, ≥0.16t to ≤0.19t, ≥0.17t to ≤0.19t, ≥0.18t to ≤0.19t, ≥0.14t to ≤0.18t, ≥0.15t to ≤0.18t, ≥0.16t to ≤0.18t, ≥0.17t to ≤0.18t, ≥0.14t to ≤0.17t, ≥0.15t to ≤0.17t, ≥0.16t to ≤0.17t, ≥0.14t to ≤0.16t, ≥0.15t to ≤0.16t, ≥0.14t to ≤0.15t, including any and all sub-ranges between the foregoing values.

[0135] In an embodiment, the DOC of the glass-ceramic article can be from 50 μm to 250 μm, from 75 μm to 200 μm, or from 100 μm to 200 μm. According to some embodiments, the DOC of the glass-ceramic article can be 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, 210 μm, 220 μm, 230 μm, 240 μm, 250 μm, and any DOC level between the foregoing values.

[0136] Exemplary electronic devices incorporating any of the glass-ceramic articles disclosed herein are as Figure 2A and 2B shown. Specifically, Figure 2A and 2B show a consumer electronic device 200 (e.g., a mobile device) that includes a housing 202 having a front surface 204, a rear surface 206, and side surfaces 208; electrical components (not shown) that are at least partially within or fully within the housing and that at least include a controller, a memory, and a display 210 at or near the front surface of the housing; and a cover substrate 212 that is located at or above the front surface of the housing such that it is located above the display. In an embodiment, at least a portion of at least one of the cover substrate 212 and the housing 202 can include any of the glass-ceramic articles disclosed herein.

[0137] Examples

[0138] The embodiments described in the present disclosure are further illustrated by the following examples.

[0139] Example 1

[0140] In this example, a series of ceramization conditions were evaluated for developing glass-ceramic articles (see Table 2 above) from two (2) glass precursor compositions (Example D1 and Example D2) derived from the present disclosure. For each precursor glass composition, a sample of the precursor glass was placed in a box furnace, the box furnace was heated to a first temperature (“nucleation temperature”) and held at the first temperature for 4 hours. The box furnace was then heated to a second higher temperature (“crystallization temperature”) and held at the second temperature for 4 hours, and then cooled. The phase composition obtained in the ceramized samples was measured by XRD. Some of the samples were optically polished into plane-parallel samples with a thickness of 0.5 mm, and the color and opacity were measured. In addition, the fracture toughness (K IC ) of the ceramized glass-ceramic articles was measured according to the V-notch short bar method.

[0141] The phase combinations obtained in the glass-ceramic articles derived from the precursor glass compositions of Examples D1 and D2 (ceramified via various ceramization cycles), and the fracture toughness of these samples are listed in Table 3 below. The color and opacity measured on the samples on black and white backgrounds are also presented in Table 4.

[0142] It can be clearly seen from Table 3 that the ceramified glass-ceramic articles from the precursor glass composition of Example D2 show lithium disilicate (Li2Si2O5) and β-spodumene as the main phases, as well as lesser amounts of lithium phosphate (Li3PO4), ZrO2 (tetragonal and / or baddeleyite) phases. There are also small amounts of zircon (ZrSiO4), K2Zr2O5, and nosean, and these secondary phases are not present in the glass-ceramic articles derived from the precursor glass composition of Example D1. Note that although the glass wt% is reported as 0.0 wt%, it is believed that there is a certain amount of residual glass phase in the material, but the amount cannot be accurately calculated by the Rietveld method. The actual wt% of the glass phase is believed to be <5 wt%.

[0143] Now referring Figure 3 , an x-ray diffraction (XRD) spectrum of the glass-ceramic article of the present example is provided. The glass-ceramic article is derived from the precursor glass composition of Example D2 and is ceramified by nucleating at 740 °C for 4 hours and crystallizing at 890 °C for 4 hours. The phase combination of the glass-ceramic is as Figure 3 shown.

[0144] It can also be clearly seen from Table 3 that the fracture toughness (K IC ) measured on the glass-ceramic articles derived from the precursor glass composition of Example D2 is about 1.65 MPa×m 1 / 2 or greater, and for samples ceramified by nucleating at 700 °C or 740 °C for 4 hours and crystallizing at 890 °C for 4 hours, the fracture toughness is up to 1.91 MPa×m 1 / 2 . For the glass-ceramic articles derived from the precursor glass composition of Example D1, the fracture toughness values are from 1.54 MPa×m 1 / 2 to 1.72 MPa×m 1 / 2 . Without being bound by theory, it is believed that the relatively high amount of lithium disilicate phase present in these glass-ceramic articles contributes to their higher level of fracture toughness compared to other glass-ceramic articles in the LAS family.

[0145] It can be clearly seen from Table 4 that the opacity of the glass-ceramic products derived from the precursor glass composition of Example D2 is in the range of 77 to 93%. The color displays of these glass-ceramic products on black and white backgrounds show an L* range between 85 and 97, an a* range between -1.5 and 0, and a b* range between -8 and 0. Table 3 - Phase composition of glass-ceramic products derived from precursor glass compositions at different nucleation and crystallization temperatures

[0146]

[0147] Table 4 - Color and opacity of glass-ceramic products derived from precursor glass compositions at different nucleation and crystallization temperatures

[0148]

[0149] Example 2

[0150] In this example, the glass-ceramic products are derived from the precursor glass compositions of the present disclosure (Example D1 and Example D2) as follows: Example 2A, the precursor glass of Example D1 is nucleated at 800 °C for 4 hours and crystallized at 875 °C for 4 hours; Example 2B, the precursor glass of Example D2 is nucleated at 740 °C for 4 hours and crystallized at 890 °C for 4 hours; and Example 2C, the precursor glass of Example D2 is nucleated at 760 °C for 4 hours and crystallized at 890 °C for 4 hours. The color and opacity data measured for the samples from this example on black and white backgrounds are listed in Table 5 below.

[0151] It is worth noting that the glass-ceramic products derived from the precursor glass composition of Example D2 (Examples 2B and 2C) show higher opacity than the glass-ceramic products derived from the precursor glass composition of Example D1 (Example 2A).

[0152] Table 5 - Color and opacity of glass-ceramic products with a thickness of 0.5 mm derived from precursor glass compositions at different nucleation and crystallization temperatures

[0153]

[0154] The Young's modulus, shear modulus, and Poisson's ratio measured for the glass-ceramic samples from this example using resonant ultrasound spectroscopy according to ASTM E2001-13 are listed in Table 6 below. The fracture toughness (K IC ) values are also presented in Table 6, which are measured using the V-notch short bar test method described in ASTM E1304-97. It can be clearly seen from this table that the mechanical properties of the glass-ceramic samples derived from the precursor glass compositions of Example D1 and Example D2 are similar.

[0155] Table 6 - Mechanical properties of glass-ceramic products derived from precursor glass compositions

[0156]

[0157] Now referring to Figure 4A , a box plot of the Knoop hardness levels of three sets of glass-ceramic articles (Examples 2A - 2C) of the present example is provided. It can be clearly seen from Figure 4A that the glass-ceramic articles of the present example derived from the precursor glass compositions of Example D1 or Example D2 exhibit similar average Knoop hardness levels of 561, 562, and 564 kg / mm 2 .

[0158] Example 3

[0159] In the present example, the glass-ceramic articles of the previous example (Examples 2A - 2C) were subjected to ion-exchange treatment for chemical strengthening. In particular, these articles were chemically strengthened by ion-exchange by placing them in a molten salt bath containing NaNO3 and KNO3 for a predetermined period of time. In the glass-ceramic articles derived from the Example D2 glass precursor composition, a depth of layer (DOL) (which is determined according to the resulting Na2O and K2O concentration profiles (see Figure 4B and 4C )) less than about 24% of the article thickness can be achieved, where the glass-ceramic articles are ceramized under the conditions of nucleation at 740 °C / 4 h and crystallization at 890 °C / 4 h or nucleation at 760 °C / 4 h and crystallization at 890 °C / 4 h, and then ion-exchanged in a 60% KNO3 / 40% NaNO3 molten salt bath at 500 °C for 4 hours to obtain 0.5 mm thick articles (Examples 2B1 and 2C1 respectively). This DOL is similar to the DOL obtained on the glass-ceramic articles derived from the Example D1 glass precursor composition, which are ceramized by nucleation at 800 °C / 4 h and crystallization at 875 °C / 4 h and ion-exchanged under the same conditions (Example 2A1). In addition, in the present example, a small amount of lithium nitrate (0.01 - 1 wt%) was added to the molten salt bath before ion-exchange to avoid the formation of an amorphous layer at the sample surface.

[0160] It can be clearly seen from the present example that forming a compressive stress zone is beneficial for achieving better mechanical properties compared to non-ion-exchanged materials. Now referring to Figure 4B and 4C , the depth-dependent microprobe distributions of Na2O and K2O concentrations in the glass-ceramic articles of the previous example (Examples 2A1 - 2C1) subjected to the ion-exchange treatment of the present example are provided respectively. In addition, from Figure 4B and 4CIt can be clearly seen that in these samples, a compressive stress zone containing at least 0.1 mol% K2O is formed at a depth of 10 μm or less from the main surface of the article.

[0161] Example 4

[0162] In this example, the microstructures of glass-ceramic articles derived from the precursor glass compositions of Example D1 and Example D2 were evaluated. The glass-ceramic articles were nucleated at 800 °C for 4 hours and crystallized at 875 °C for 4 hours, and ceramified by nucleation at 700 °C for 4 hours and crystallization at 890 °C for 4 hours (Examples 3B and 3A, respectively). Refer to Figure 5A and 5B , which provide the microstructure of Example 3A in the form of scanning electron microscope (SEM) images. It can be clearly seen from these figures that the white dots correspond to the ZrO2 phase, the needle-shaped needles correspond to lithium disilicate, the black dots correspond to lithium phosphate, and the large gray blocks correspond to the β-spodumene solid solution.

[0163] Now refer to Figure 5C and 5D , which provide SEM images of two glass-ceramic articles (Examples 3A and 3B) of this example. Specifically, in Figure 5C and 5D , the Figure 5A and 5B microstructure (i.e., from Example 3A) was compared in detail with the microstructures of other glass-ceramic articles of this example (Example 3B).

[0164] From Figure 5A - 5D it can be clearly seen that the improved glass-ceramics presented in the present disclosure exhibit a combination of crystalline phases composed of: β-spodumene solid solution crystals in the range of 0.5 to 2 μm, lithium disilicate needles with a length of 0.5 to 2 μm and a width of 100 to 500 nm, uniformly dispersed Zr-based crystals (tetragonal zirconia, zircon, K2Zr2O5) in the range of 50 to 500 nm, and lithium phosphate crystals in the range of 50 to 500 nm. Further refer to Figure 5C and 5D (for Examples 3A and 3B), where the white dots correspond to the ZrO2 phase, the needle-shaped needles correspond to lithium disilicate, the black dots correspond to lithium phosphate, and the large gray blocks correspond to the β-spodumene solid solution. In addition, the percentages of these crystalline phases present in the glass-ceramic articles of this example are also shown in these figures.

[0165] Example 5

[0166] In this example, the precursor glass compositions according to the present disclosure (from Examples D1 and D2) are melted or remelted as specified in Examples 4A - 4C of this example. Table 7 below lists the precursor compositions of this example, their melting conditions, and their measured β-OH contents. As Figure 6A shown, for the glass compositions in Table 7 and this example with different measured β-OH contents, plots of transmittance versus wave number in the near-infrared (NIR) spectrum are provided. The β-OH content is proportional to the absorption measured at a wave number of 3500 cm -1 as a ratio to the baseline reference portion of the spectrum, which is taken at 3846 cm -1 . Finally, these melted precursor glass compositions can be ceramified according to the method of the present disclosure to obtain glass-ceramic articles.

[0167] Table 7 - Comparison of β-OH Contents in Melted and Remelted Precursor Glass Compositions

[0168]

[0169] Now referring to Figure 6B , differential scanning calorimetry (DSC) plots of two glass compositions (Examples 4A and 4B) with different β-OH contents in this example are provided. Example 4A glass derived from the Example D2 precursor glass composition and the remelt of the glass with different β-OH levels (Example 4B) also show differences in crystallization behavior, which can be seen from the differences in the intensity and peak temperature of the exothermic events (crystallization) in the range of 700 - 800 °C. Although this temperature range is known to be associated with lithium silicate phases in this family of compositions and not specifically with zirconia, it emphasizes that the same glass composition with different β-OH levels can exhibit different crystallization behaviors. In particular, during the subsequent ceramification process, an increased water content may lead to a decrease in the maximum growth temperature.

[0170] Example 5A

[0171] In this example, after ceramization by nucleating at 700 °C / 4 h and crystallizing at 875 °C / 4 h, XRD Rietveld analysis was performed on the Example 4A glass from the previous example and the remelted Example 4A glass (Example 4B). Glasses with high or low iron (Fe) and potassium (K) ion contents, which are compositionally similar to Example 4A, were also evaluated, as were the remelts of these glasses ceramized under the same ceramization conditions (i.e., nucleated at 700 °C / 4 h and crystallized at 875 °C / 4 h). Generally, the remelts of these glasses have a lower β-OH content. The results of these analyses are presented in Table 8 below. As can be seen from Table 8, for a given ceramization cycle (which is 700 °C / 4 h + 875 °C / 4 h), the remelts do systematically show a lower total amount of ZrO2.

[0172] Table 8 - XRD Rietveld analysis (wt%) of Example D2 precursor glasses and their remelts (ceramized by nucleating at 700 °C / 4 h and crystallizing at 875 °C / 4 h)

[0173]

[0174] Now referring to Figure 7A , a plot of the opacity of three glass-ceramic articles (Examples 4A, 4A1, and 4A2) of this example versus the amount of ZrO2 is provided. As Figure 7A shown, the opacity of the glass-ceramics obtained in these white glass-ceramics derived from the Example D2 precursor glass composition is proportional to the amount of ZrO2 precipitated during the ceramization cycle. Thus, when ceramized with the same ceramization cycle, glasses with a lower β-OH produce less opaque glass-ceramics than glasses with the same composition but a higher β-OH.

[0175] Now referring to Figure 7B , a plot of the amount of secondary phase as a function of time, generated by XRD, during the growth / crystallization stage of the ceramization cycle at 875 °C for two glass-ceramic articles (Examples 4A and 4B) of this example is provided. It should be noted that each sample was ceramized at the specified temperature and duration, cooled to room temperature, and then evaluated using XRD. Figure 7B shows the evolution of the secondary phase during the 875 °C growth / crystallization step for the glass-ceramic derived from the precursor glass with a higher β-OH content (Example 4A) and the glass-ceramic derived from the precursor glass with a lower β-OH content (Example 4B, the remelt of Example 4A). In particular, Figure 7B shows that less ZrO2 is precipitated in Example 4B (with a lower β-OH content) compared to Example 4A during the ceramization cycle.

[0176] Example 5B

[0177] In this example, the variation of the ZrO2 level obtained in the glass-ceramic product with the β-OH content in the precursor glass composition and the ceramization cycle was studied. Refer to Figure 8A (2θ from 0° to 55°) and 8B (2θ from 25° to 35°), XRD spectra of the glass-ceramic product of Example 4B from a previous example were provided. The glass-ceramic product was nucleated at 760 °C / 4 h and crystallized at 875 °C / 4 h for ceramization (named Example 4B1); nucleated at 740 °C / 4 h and crystallized at 875 °C / 4 h for ceramization (named Example 4B2); and nucleated at 700 °C / 4 h and crystallized at 875 °C / 4 h for ceramization (named Example 4B3). These results were compared with the spectra of the glass-ceramic product of Example 4A from a previous example, which was also nucleated at 740 °C / 4 h and crystallized at 875 °C / 4 h for ceramization.

[0178] From Figure 8A and 8B it can be clearly seen that there is a significant difference in the amount of ZrO2 precipitated between the glass-ceramic product of Example 4B3 and the glass-ceramic of Example 4A (both ceramized at 700 °C / 4 h + 875 °C / 4 h but derived from precursor glass compositions with different β-OH contents) based on the observed ZrO2 peak intensity. When the nucleation temperature of the glass-ceramic product of Example 4B2 was increased to 740 °C, a similar amount of ZrO2 could be obtained compared with the glass-ceramic product of Example 4A. In addition, it is obvious that in the glass-ceramic product of Example 4B1, further increasing the nucleation temperature to 760 °C results in an even higher ZrO2 concentration.

[0179] Example 6

[0180] In this example, the variation of the total ZrO2 content of the glass-ceramic products (Examples 4A and 4C from a previous example) with the nucleation temperature employed in the ceramization cycle was studied. The glass-ceramic products were derived from either of two glass precursor compositions with different β-OH contents (i.e., Example D1 and Example D2). Refer to Figure 9 , a graph showing the variation of the ZrO2 amount with the nucleation temperature for the glass-ceramic products (Examples 4A and Example 4C) derived from two glass precursor compositions (Example D1 and Example D2) according to an embodiment of the present disclosure was provided. The detailed results are also provided in Table 9 below.

[0181] Table 9 - XRD Rietveld data of the glass-ceramic products (ceramized by nucleating for 4 hours at different nucleation temperatures and crystallizing at 875 °C for 4 hours) derived from the precursor glass compositions of Examples 4A and 4C

[0182]

[0183] As can be clearly seen from Table 9 and Figure 9 it is evident that for any given ceramization cycle, compared to the example D1 precursor glass composition with a lower β-OH content (i.e., the example 4C glass-ceramic article), more total ZrO2 is obtained from the glass-ceramic article derived from the example D2 precursor glass composition (i.e., the example 4A glass-ceramic article). For both of these precursor glass compositions, an increased nucleation temperature results in an increased ZrO2 concentration in the resulting glass-ceramic article.

[0184] It can also be seen from Table 9 that when the nucleation temperature is higher than 700 °C, high quartz precipitates in the glass-ceramic article derived from the example D2 precursor glass composition. However, when the nucleation temperature exceeds 780 °C, the high quartz phase only appears in the glass-ceramic article derived from the example D1 precursor glass composition. Thus, between the glass-ceramic articles derived from these two precursor glass compositions, the threshold for high quartz nucleation is shifted by approximately 80 °C. Additionally, it is evident from Table 9 that the phase assemblage of the glass-ceramic article sourced from the example D1 precursor glass composition nucleated at 800 °C is very similar to the phase assemblage of the glass-ceramic article sourced from the example D2 precursor glass composition nucleated at 760 °C.

[0185] Therefore, the behavior of these two precursor glass compositions (example D1 with a lower β-OH content and example D2 with a higher β-OH content) during the above ceramization cycle is similar in nature. However, this behavior appears to change, and a higher nucleation temperature is required to obtain the same crystallization pattern. Thus, it is evident that when starting with different precursor glass compositions having different β-OH contents, the ceramization cycle can be adjusted to obtain similar glass-ceramic articles. For example, compared to the glass-ceramic article derived from a precursor glass composition with a higher β-OH content, the precursor glass composition of the present disclosure having a lower β-OH content can be ceramized at a higher nucleation temperature to achieve similar ZrO2 and opacity.

[0186] Example 6A

[0187] It can be clearly seen from this example that the color and opacity of the white glass-ceramic articles of the present disclosure can depend on the crystallization phase assemblage resulting from the ceramization cycle. As shown in Table 10 below, the color and opacity of the glass-ceramic article (named example 4A) (0.8 mm thickness) derived from the example D2 precursor glass composition are reported, and the glass-ceramic article undergoes the ceramization process shown in the table.

[0188] It can also be clearly seen from this example, especially from Table 11 below, that for a given ceramization cycle, controlling the β-OH concentration in the precursor glass helps to produce glass-ceramic articles with different colors and opacities. Table 11 provides the color coordinates and opacities of glass-ceramic articles (designated as Example 4C and Example 4A respectively) (0.8 mm thickness) derived from the precursor glass compositions of Example D1 and Example D2. In addition, as detailed in Table 11, these glass-ceramic articles were subjected to the same ceramization cycle, except that the nucleation temperature was varied from 700 °C to 800 °C.

[0189] Table 10 - Color coordinates and opacities measured on glass-ceramic articles (Example 4A) derived from the precursor glass composition of Example D2, which were subjected to different ceramization conditions

[0190]

[0191]

[0192] Table 11 - Color coordinates and opacities measured on glass-ceramic articles (Example 4A and Example 4C) derived from the precursor glass compositions of Example D2 and Example D1, which were subjected to different ceramization conditions

[0193]

[0194] The various features described in the specification can be combined in any and all combinations, for example, as listed in the following examples.

[0195] Aspect 1. A glass-ceramic article is provided, which comprises (in mol%):

[0196] 68 - 70% SiO2;

[0197] 3.5 - 4.5% Al2O3;

[0198] 0.5 - 1.5% P2O5;

[0199] 20 - 24% Li2O;

[0200] 0 - 0.5% Na2O;

[0201] 0 - 0.5% K2O;

[0202] 2.5 - 3.1% ZrO2;

[0203] 0.5 - 1.0% CaO;

[0204] 0 - 0.2% Fe2O3;

[0205] 0 - 0.2% HfO₂; and

[0206] 0.001 - 0.2% SnO₂. The glass - ceramic article is opaque and further comprises a lithium disilicate crystal phase, a β - spodumene solid - solution crystal phase, a Zr - based crystal phase, and a lithium phosphate crystal phase.

[0207] Aspect 2. A glass - ceramic article according to aspect 1, wherein the glass - ceramic article further has an opacity of about 75 to 95%, as measured by a glass - ceramic article having a thickness of about 0.5 mm.

[0208] Aspect 3. A glass - ceramic article according to aspect 1 or aspect 2, wherein the glass - ceramic article further has a reflected color given by L* from 80 to 98, a* from - 2.0 to 0, and b* from - 10.0 to 0 (CIE L*, a*, and b* coordinate system).

[0209] Aspect 4. A glass - ceramic article according to any one of aspects 1 to 3, wherein the glass - ceramic article further has a fracture toughness (K 1 / 2 ) of 1.0 to 3.0 MPa×m IC , as measured by the V - notch short - bar method.

[0210] Aspect 5. A glass - ceramic article according to any one of aspects 1 to 3, wherein the glass - ceramic article further has a fracture toughness (K 1 / 2 ) of 1.5 to 3.0 MPa×m IC , as measured by the V - notch short - bar method.

[0211] Aspect 6. A glass - ceramic article according to any one of aspects 1 to 5, wherein the lithium disilicate crystal phase comprises needles having a length of 0.5 to 2 μm and a width of 100 to 500 nm, the β - spodumene crystal phase comprises crystals having a size of 0.5 to 2 μm, the Zr - based crystal phase comprises crystals having a size of 50 to 500 nm, and the lithium phosphate crystal phase comprises crystals having a size of 50 to 500 nm.

[0212] Aspect 7. A glass - ceramic article according to any one of aspects 1 to 6, which further comprises a compressive stress zone that comprises at least 0.1 mol% K₂O at a depth of 10 μm or less from the main surface of the glass - ceramic article, and a depth of layer (DOL) less than or equal to 0.24×t, where t is the thickness of the glass - ceramic article.

[0213] Aspect 8. Provide a glass-ceramic article according to any one of Aspects 1 to 7, wherein the glass-ceramic article further has a Knoop hardness greater than 500 kgf / mm 2 and an elastic modulus greater than 95 GPa.

[0214] Aspect 9. Provide a glass-ceramic article comprising (in mol%):

[0215] 70 - 72% SiO2;

[0216] 3.5 - 4.5% Al2O3;

[0217] 0.5 - 1.5% P2O5;

[0218] 20 - 24% Li2O;

[0219] 0 - 0.5% Na2O;

[0220] 0 - 0.5% K2O;

[0221] 1.7 - 2.3% ZrO2;

[0222] 0 - 0.5% CaO;

[0223] 0 - 0.2% Fe2O3;

[0224] 0 - 0.2% HfO2; and

[0225] 0.001 - 0.2% SnO2. The glass-ceramic article is opaque and contains a β-spodumene solid-solution crystalline phase, a lithium disilicate crystalline phase, and one or more ZrO2-containing crystalline phases. In addition, the glass-ceramic article is derived from a glass precursor having a β-OH content of 0.1 / mm to 0.5 / mm.

[0226] Aspect 10. Provide a glass-ceramic article according to Aspect 9 or any preceding aspect, wherein the glass-ceramic article is derived from a glass precursor having a β-OH content of 0.15 / mm to 0.4 / mm.

[0227] Aspect 11. Provide a glass-ceramic article according to Aspect 9 or Aspect 10 or any preceding aspect, wherein the glass-ceramic article further has an opacity of about 60 to 97%, as measured through a glass-ceramic article having a thickness of about 0.5 mm.

[0228] Aspect 12. Provide a glass-ceramic article according to any one of Aspects 9 to 11 or any preceding aspect, wherein the glass-ceramic article further has a reflected color given by L* of 85 to 98, a* of -3.0 to +3.0, and b* of -5.0 to +5.0 (CIEL*, a*, and b* coordinate system).

[0229] Aspect 13. Provide a glass-ceramic article according to any one of aspects 9 to 12 or any of the foregoing aspects, wherein the glass-ceramic article further has a fracture toughness (K 1 / 2 ) of 1.0 to 3.0 MPa×m IC , as measured by the V-notch short rod method.

[0230] Aspect 14. Provide a glass-ceramic article according to any one of aspects 9 to 13 or any of the foregoing aspects, wherein in the glass-ceramic article, the one or more ZrO2-containing crystalline phases total 0.5 to 4.0% by weight, as determined by Rietveld analysis of the x-ray diffraction (XRD) data of the glass-ceramic article.

[0231] Aspect 15. Provide a glass-ceramic article according to any one of aspects 9 to 14 or any of the foregoing aspects, which further comprises a compressive stress zone that comprises at least 0.1 mol% K2O at a depth of 10 μm or less from the main surface of the glass-ceramic article, and a depth of layer (DOL) that is less than or equal to 0.24×t, where t is the thickness of the glass-ceramic article.

[0232] Aspect 16. Provide a glass-ceramic article according to any one of aspects 9 to 15 or any of the foregoing aspects, wherein the glass-ceramic article further has a Knoop hardness greater than 500 kgf / mm 2 and an elastic modulus greater than 95 GPa.

[0233] Aspect 17. Provide a glass-ceramic article that comprises (in mol%):

[0234] 67 - 74% SiO2;

[0235] 2 - 6% Al2O3;

[0236] 0.5 - 1.5% P2O5;

[0237] 18 - 25% Li2O;

[0238] 0 - 1% Na2O;

[0239] 0 - 1% K2O;

[0240] 1 - 4% ZrO2;

[0241] 0 - 2% CaO; and

[0242] 0.001 - 0.5% SnO₂. The glass-ceramic article is opaque and further contains a lithium disilicate crystal phase, a β-spodumene solid solution crystal phase, a Zr-based crystal phase, and a lithium phosphate crystal phase.

[0243] Aspect 18. Provide the glass-ceramic article according to aspect 17 or any of the preceding aspects, wherein the glass-ceramic article further has a fracture toughness (K 1 / 2 ) of 1.0 to 3.0 MPa×m IC , as measured by the V-notch short rod method, and an opacity of about 60 to 97%, as measured by a glass-ceramic article having a thickness of about 0.5 mm.

[0244] Aspect 19. Provide the glass-ceramic article according to aspect 17 or aspect 18 or any of the preceding aspects, wherein the glass-ceramic article further has a reflected color given by L* of 80 to 98, a* of -3.0 to +3.0, and b* of -10.0 to +5.0 (CIEL*, a*, and b* coordinate system).

[0245] Aspect 20. Provide the glass-ceramic article according to any one of aspects 17 to 19 or any of the preceding aspects, wherein the glass-ceramic article contains a β-spodumene solid solution crystal phase, a lithium disilicate crystal phase, and one or more ZrO₂-containing crystal phases.

[0246] Aspect 21. Provide the glass-ceramic article according to any one of aspects 17 to 20 or any of the preceding aspects, wherein the glass-ceramic article is derived from a glass precursor having a β-OH content of 0.1 / mm to 0.5 / mm.

[0247] Aspect 22. Provide the glass-ceramic article according to any one of aspects 17 to 21 or any of the preceding aspects, which further contains a compressive stress zone that contains at least 0.1 mol% K₂O at a depth of 10 μm or less from the main surface of the glass-ceramic article, and a depth of layer (DOL) less than or equal to 0.24×t, where t is the thickness of the glass-ceramic article.

[0248] Aspect 23. Provide the glass-ceramic article according to any one of aspects 17 to 22 or any of the preceding aspects, wherein the glass-ceramic article further has a Knoop hardness greater than 500 kgf / mm 2 and an elastic modulus greater than 95 GPa.

[0249] Aspect 24. A glass-ceramic article, which contains (in mol%):

[0250] 67 - 74% SiO₂;

[0251] 2 - 6% Al₂O₃;

[0252] 0.5 - 1.5% P2O5;

[0253] 18 - 25% Li2O;

[0254] 0 - 1% Na2O;

[0255] 0 - 1% K2O;

[0256] 1 - 4% ZrO2;

[0257] 0 - 2% CaO; and

[0258] 0.001 - 0.5% SnO2,

[0259] wherein the glass - ceramic article is opaque, and

[0260] further wherein the glass - ceramic article comprises a lithium disilicate crystal phase, a β - spodumene solid - solution crystal phase, a Zr - based crystal phase, and a lithium phosphate crystal phase.

[0261] Aspect 25. The glass - ceramic article according to aspect 24 or any of the preceding aspects, wherein the glass - ceramic article further has a fracture toughness (K 1 / 2 ) of 1.0 to 3.0 MPa×m IC as measured by the V - notch short - rod method, and further wherein the glass - ceramic article has an opacity of 60 to 97% as measured by a glass - ceramic article having a thickness of 0.5 mm.

[0262] Aspect 26. The glass - ceramic article according to aspect 24 or aspect 25 or any of the preceding aspects, wherein the glass - ceramic article further has a reflected color given by L* of 80 to 98, a* of - 3.0 to + 3.0, and b* of - 10.0 to + 5.0 (CIE L*, a*, and b* color coordinate system).

[0263] Aspect 27. The glass - ceramic article according to any one of aspects 24 to 26 or any of the preceding aspects, wherein the glass - ceramic article comprises a β - spodumene solid - solution crystal phase, a lithium disilicate crystal phase, and one or more ZrO2 - containing crystal phases.

[0264] Aspect 28. The glass - ceramic article according to any one of aspects 24 to 27 or any of the preceding aspects, wherein the glass - ceramic article is derived from a glass precursor having a β - OH content of 0.1 / mm to 0.5 / mm.

[0265] Aspect 29. The glass - ceramic article according to any one of aspects 24 to 28 or any of the preceding aspects, which further comprises:

[0266] a compressive stress zone that contains at least 0.1 mol% K2O at a depth of 10 μm or less from the main surface of the glass-ceramic article; and

[0267] a depth of layer (DOL) less than or equal to 0.24×t, where t is the thickness of the glass-ceramic article.

[0268] Aspect 30. The glass-ceramic article according to any one of aspects 24 to 29 or any of the foregoing aspects, wherein the glass-ceramic article further has a Knoop hardness greater than 500 kgf / mm 2 and an elastic modulus greater than 95 GPa.

[0269] Aspect 31. The glass-ceramic article according to any one of aspects 24 to 30 or any of the foregoing aspects, wherein the glass-ceramic article further comprises (in mol%):

[0270] 70 - 72% SiO2;

[0271] 3.5 - 4.5% Al2O3;

[0272] 0.5 - 1.5% P2O5;

[0273] 20 - 24% Li2O;

[0274] 0 - 0.5% Na2O;

[0275] 0 - 0.5% K2O;

[0276] 1.7 - 2.3% ZrO2;

[0277] 0 - 0.5% CaO;

[0278] 0 - 0.2% Fe2O3;

[0279] 0 - 0.2% HfO2; and

[0280] 0.001 - 0.2% SnO2.

[0281] Aspect 32. The glass-ceramic article according to aspect 31 or any of the foregoing aspects, wherein the glass-ceramic article is derived from a glass precursor having a β-OH content of 0.15 / mm to 0.4 / mm.

[0282] Aspect 33. The glass-ceramic article according to aspect 31 or aspect 32 or any of the foregoing aspects, wherein the glass-ceramic article further has an opacity of 60 to 97%, as measured by a glass-ceramic article having a thickness of 0.5 mm.

[0283] Aspect 34. The glass-ceramic article according to any one of aspects 31 to 33 or any of the foregoing aspects, wherein the glass-ceramic article further has a reflected color given by L* of 85 to 98, a* of -3.0 to +3.0, and b* of -5.0 to +5.0 (CIE L*, a*, and b* coordinate system).

[0284] Aspect 35. The glass-ceramic article according to any one of aspects 24 to 30 or any of the foregoing aspects, wherein the glass-ceramic article further comprises (in mol%):

[0285] 68 - 70% SiO2;

[0286] 3.5 - 4.5% Al2O3;

[0287] 0.5 - 1.5% P2O5;

[0288] 20 - 24% Li2O;

[0289] 0 - 0.5% Na2O;

[0290] 0 - 0.5% K2O;

[0291] 2.5 - 3.1% ZrO2;

[0292] 0.5 - 1.0% CaO;

[0293] 0 - 0.2% Fe2O3;

[0294] 0 - 0.2% HfO2; and

[0295] 0.001 - 0.2% SnO2.

[0296] Aspect 36. The glass-ceramic article according to aspect 35 or any of the foregoing aspects, wherein the glass-ceramic article further has an opacity of 75 to 95%, as measured by a glass-ceramic article with a thickness of 0.5 mm.

[0297] Aspect 37. The glass-ceramic article according to aspect 35 or aspect 36 or any of the foregoing aspects, wherein the glass-ceramic article further has a reflected color given by L* of 80 to 98, a* of -2.0 to 0, and b* of -10.0 to 0 (CIE L*, a*, and b* coordinate system).

[0298] Aspect 38. The glass-ceramic article according to any one of aspects 35 to 37 or any of the foregoing aspects, wherein the glass-ceramic article further has a fracture toughness (K 1 / 2 ) of 1.5 to 3.0 MPa×m IC , as measured by the V-notch short rod method.

[0299] Aspect 39. A glass-ceramic article comprising (in mol%):

[0300] 67 - 74% SiO2;

[0301] 2 - 6% Al2O3;

[0302] 0.5 - 1.5% P2O5;

[0303] 18 - 25% Li2O;

[0304] 0 - 1% Na2O;

[0305] 0 - 1% K2O;

[0306] 1 - 4% ZrO2;

[0307] 0 - 2% CaO; and

[0308] 0.001 - 0.5% SnO2,

[0309] wherein the glass-ceramic article is opaque, and

[0310] further wherein the glass-ceramic article comprises a lithium disilicate crystalline phase, a β-spodumene solid solution crystalline phase, a Zr-based crystalline phase, and a lithium phosphate crystalline phase.

[0311] Aspect 40. The glass-ceramic article according to aspect 39 or any preceding aspect, wherein the glass-ceramic article further has a fracture toughness (K 1 / 2 ) of 1.0 to 3.0 MPa×m IC as measured by the V-notch short rod method, and further wherein the glass-ceramic article has an opacity of 60 to 97% as measured by a glass-ceramic article having a thickness of 0.5 mm.

[0312] Aspect 41. The glass-ceramic article according to aspect 39 or aspect 40 or any preceding aspect, wherein the glass-ceramic article further has a reflected color given by L* of 80 to 98, a* of -3.0 to +3.0, and b* of -10.0 to +5.0 (CIE L*, a*, and b* color coordinate system).

[0313] Aspect 42. The glass-ceramic article according to any one of aspects 39 to 41 or any preceding aspect, wherein the glass-ceramic article comprises a β-spodumene solid solution crystalline phase, a lithium disilicate crystalline phase, and one or more ZrO2-containing crystalline phases.

[0314] Aspect 43. The glass-ceramic article according to any one of aspects 39 to 42 or any of the foregoing aspects, wherein the glass-ceramic article is derived from a glass precursor having a β-OH content of 0.1 / mm to 0.5 / mm.

[0315] Aspect 44. The glass-ceramic article according to any one of aspects 39 to 43 or any of the foregoing aspects, further comprising:

[0316] A compressive stress zone that contains at least 0.1 mol% K2O at a depth of 10 μm or less from the main surface of the glass-ceramic article; and

[0317] A depth of layer (DOL) less than or equal to 0.24×t, where t is the thickness of the glass-ceramic article.

[0318] Aspect 45. The glass-ceramic article according to any one of aspects 39 to 44 or any of the foregoing aspects, wherein the glass-ceramic article further comprises (in mol%):

[0319] 70 - 72% SiO2;

[0320] 3.5 - 4.5% Al2O3;

[0321] 0.5 - 1.5% P2O5;

[0322] 20 - 24% Li2O;

[0323] 0 - 0.5% Na2O;

[0324] 0 - 0.5% K2O;

[0325] 1.7 - 2.3% ZrO2;

[0326] 0 - 0.5% CaO;

[0327] 0 - 0.2% Fe2O3;

[0328] 0 - 0.2% HfO2; and

[0329] 0.001 - 0.2% SnO2.

[0330] Aspect 46. The glass-ceramic article according to aspect 45 or any of the foregoing aspects, wherein the glass-ceramic article is derived from a glass precursor having a β-OH content of 0.15 / mm to 0.4 / mm.

[0331] Aspect 47. The glass-ceramic article according to any one of aspects 39 to 43 or any of the foregoing aspects, wherein the glass-ceramic article further comprises (in mol%):

[0332] 68 - 70% SiO2;

[0333] 3.5 - 4.5% Al2O3;

[0334] 0.5 - 1.5% P2O5;

[0335] 20 - 24% Li2O;

[0336] 0 - 0.5% Na2O;

[0337] 0 - 0.5% K2O;

[0338] 2.5 - 3.1% ZrO2;

[0339] 0.5 - 1.0% CaO;

[0340] 0 - 0.2% Fe2O3;

[0341] 0 - 0.2% HfO2; and

[0342] 0.001 - 0.2% SnO2.

[0343] Aspect 48. The glass - ceramic article according to aspect 47 or any of the preceding aspects, wherein the glass - ceramic article further has an opacity of 75 to 95%, as measured by a glass - ceramic article having a thickness of 0.5 mm.

Claims

1. A glass-ceramic article, comprising (in mol%): 68 - 70% SiO2; 3.5 - 4.5% Al2O3; 0.5 - 1.5% P2O5; 20 - 24% Li2O; 0 - 0.5% Na2O; 0 - 0.5% K2O; 2.5 - 3.1% ZrO2; 0.5 - 1.0% CaO; 0 - 0.2% Fe2O3; 0 - 0.2% HfO2; and 0.001 - 0.2% SnO2, wherein the glass-ceramic article is opaque, and further wherein the glass-ceramic article comprises a lithium disilicate crystalline phase, a β-spodumene solid solution crystalline phase, a Zr-based crystalline phase, and a lithium phosphate crystalline phase.

2. The glass-ceramic article according to claim 1, wherein the glass-ceramic article further has an opacity of 75 to 95%, as measured by a glass-ceramic article having a thickness of 0.5 mm.

3. The glass-ceramic article according to claim 1 or claim 2, wherein the glass-ceramic article further has a reflected color given by L* of 80 to 98, a* of -2.0 to 0, and b* of -10.0 to 0 (CIE L*, a*, and b* coordinate system).

4. The glass-ceramic article according to any one of claims 1 to 3, wherein the glass-ceramic article further has a fracture toughness (K 1 / 2 ) of 1.0 to 3.0 MPa×m IC , as measured by the Chevron Notch Short Bar Method.

5. The glass-ceramic article according to any one of claims 1 to 3, wherein the glass-ceramic article further has a fracture toughness (K 1 / 2 ) of 1.5 to 3.0 MPa×m IC , as measured by the V-notch short rod method.

6. The glass-ceramic article according to any one of claims 1 to 5, wherein the lithium disilicate crystalline phase comprises needles having a length of 0.5 to 2 μm and a width of 100 to 500 nm, the β-spodumene crystalline phase comprises crystals having a size of 0.5 to 2 μm, the Zr-based crystalline phase comprises crystals having a size of 50 to 500 nm, and the lithium phosphate crystalline phase comprises crystals having a size of 50 to 500 nm.

7. The glass-ceramic article according to any one of claims 1 to 6, which further comprises: a compressive stress zone, the compressive stress zone comprising at least 0.1 mol% K2O at a depth of 10 μm or less from the main surface of the glass-ceramic article; and a depth of layer (DOL) less than or equal to 0.24 × t, where t is the thickness of the glass-ceramic article.

8. The glass-ceramic article according to any one of claims 1 to 7, wherein the glass-ceramic article further has a Knoop hardness greater than 500 kgf / mm 2 and a modulus of elasticity greater than 95 GPa.

9. A glass-ceramic article, comprising (in mol%): 70 - 72% SiO2; 3.5 - 4.5% Al2O3; 0.5 - 1.5% P2O5; 20 - 24% Li2O; 0 - 0.5% Na2O; 0 - 0.5% K2O; 1.7 - 2.3% ZrO2; 0 - 0.5% CaO; 0 - 0.2% Fe2O3; 0 - 0.2% HfO2; and 0.001 - 0.2% SnO2, wherein the glass-ceramic article is opaque, wherein the glass-ceramic article comprises a β-spodumene solid solution crystalline phase, a lithium disilicate crystalline phase, and one or more ZrO2-containing crystalline phases, and further wherein the glass-ceramic article is derived from a glass precursor having a β-OH content of 0.1 / mm to 0.5 / mm.

10. The glass-ceramic article according to claim 9, wherein the glass-ceramic article is derived from a glass precursor having a β-OH content of 0.15 / mm to 0.4 / mm.

11. The glass-ceramic article according to claim 9 or claim 10, wherein the glass-ceramic article further has an opacity of 60 to 97%, as measured by a glass-ceramic article having a thickness of 0.5 mm.

12. The glass-ceramic article according to any one of claims 9 to 11, wherein the glass-ceramic article further has a reflected color given by L* of 85 to 98, a* of -3.0 to +3.0, and b* of -5.0 to +5.0 (CIE L*, a*, and b* coordinate system).

13. The glass-ceramic article according to any one of claims 9 to 12, wherein the glass-ceramic article further has a fracture toughness (K 1 / 2 ) of 1.0 to 3.0 MPa×m IC , as measured by the V-notch short rod method.

14. The glass-ceramic article according to any one of claims 9 to 13, wherein in the glass-ceramic article, the one or more ZrO2-containing crystalline phases total 0.5 to 4.0% by weight, as determined by Rietveld analysis of the x-ray diffraction (XRD) data of the glass-ceramic article.

15. The glass-ceramic article according to any one of claims 9 to 14, which further comprises: a compressive stress zone that contains at least 0.1 mol% K2O at a depth of 10 μm or less from the main surface of the glass-ceramic article; and a depth of layer (DOL) less than or equal to 0.24×t, where t is the thickness of the glass-ceramic article.

16. The glass-ceramic article according to any one of claims 9 to 15, wherein the glass-ceramic article further has a Knoop hardness greater than 500 kgf / mm 2 and an elastic modulus greater than 95 GPa.

17. A glass-ceramic article, which comprises (in mol%): 67 - 74% SiO2; 2 - 6% Al2O3; 0.5 - 1.5% P2O5; 18 - 25% Li2O; 0 - 1% Na2O; 0 - 1% K2O; 1 - 4% ZrO2; 0 - 2% CaO; and 0.001 - 0.5% SnO2, wherein the glass-ceramic article is opaque, and further wherein the glass-ceramic article comprises a lithium disilicate crystalline phase, a β-spodumene solid solution crystalline phase, a Zr-based crystalline phase, and a lithium phosphate crystalline phase.

18. The glass-ceramic article according to claim 17, wherein the glass-ceramic article further has a fracture toughness (K 1 / 2 ) of from 1.0 to 3.0 MPa×m IC as measured by the V-notch short bar method, and further wherein the glass-ceramic article has an opacity of from 60 to 97% as measured on a 0.5 mm thick glass-ceramic article.

19. The glass-ceramic article according to claim 17 or claim 18, wherein the glass-ceramic article further has a reflected color given by L* of 80 to 98, a* of -3.0 to +3.0, and b* of -10.0 to +5.0 (CIE L*, a*, and b* coordinate system).

20. The glass-ceramic article according to any one of claims 17 to 19, wherein the glass-ceramic article comprises a β-spodumene solid solution crystalline phase, a lithium disilicate crystalline phase, and one or more ZrO2-containing crystalline phases.

21. The glass-ceramic article according to any one of claims 17 to 20, wherein the glass-ceramic article is derived from a glass precursor having a β-OH content of 0.1 / mm to 0.5 / mm.

22. The glass-ceramic article according to any one of claims 17 to 21, which further comprises: a compressive stress zone that contains at least 0.1 mol% K2O at a depth of 10 μm or less from the main surface of the glass-ceramic article; and a depth of layer (DOL) less than or equal to 0.24×t, where t is the thickness of the glass-ceramic article.

23. The glass-ceramic article according to any one of claims 17 to 22, wherein the glass-ceramic article further has a Knoop hardness greater than 500 kgf / mm 2 and an elastic modulus greater than 95 GPa.

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