Chemically strengthened microcrystalline glass and preparation thereof

Abstract

This invention provides a chemically strengthened glass-ceramic and its preparation. The chemically strengthened glass-ceramic includes a glass-ceramic substrate and a compressive stress layer formed on the surface of the substrate through ion exchange chemical strengthening. The glass-ceramic substrate comprises crystal family 1 and crystal family 2. Crystal family 1 includes crystals having the following structural formula: (Zn x Mg 1‑x‑y Al 2‑2y (Al) 2y Mg y O4, wherein: 0≤x≤1; 0≤y≤1; and 0≤x+y≤1; the crystal group 2 includes zirconium oxide; the compressive stress layer has a CTLD_saf value of 15000~70000 MPa. Compared with the existing LAS microcrystalline glass system, the chemically strengthened microcrystalline glass of the present invention not only has excellent mechanical properties and impact resistance, but also significantly reduces the overall cost.

Description

Technical Field

[0001] This invention relates to the field of new materials technology, and in particular to the field of microcrystalline glass technology. Specifically, this invention relates to a chemically strengthened microcrystalline glass and its preparation. Background Technology

[0002] Glass-ceramics, with their superior mechanical strength, excellent scratch resistance, and high optical transmittance, have become a core material for cover plates in high-end consumer electronics products such as smartphones and tablets. Currently, technological development in this field mainly focuses on two paths: one is to optimize and deeply enhance the performance of the mature lithium aluminum silicate (LAS) glass-ceramic system; the other is to explore new crystalline phase systems with higher theoretical performance limits, among which spinel glass-ceramics are the most noteworthy.

[0003] 1. LAS (Laminated Assay) microcrystalline glass system: Performance bottlenecks and inherent limitations of mainstream technologies

[0004] The LAS (Li₂O-Al₂O₃-SiO₂) system is the cornerstone of current high-performance transparent glass-ceramics. Its core technology lies in the controllable precipitation of specific nanocrystalline phases through precise composition and heat treatment design, thereby customizing material properties. Lithium feldspar and lithium disilicate are two key host crystalline phases, but both have significant drawbacks.

[0005] Lithium-bearing feldspar type LAS microcrystalline glass: This type typically requires a Li₂O content greater than 20 mol% to precipitate a high proportion of crystals, achieving high impact strength and light transmittance, thus it is widely used in electronic device covers. However, its surface hardness and scratch resistance are relatively insufficient. A more significant problem is that the high lithium content results in a large amount of residual lithium oxide in the glass phase, severely degrading the material's chemical resistance and water resistance. Simultaneously, the soaring global price of lithium resources also puts it under extremely high raw material cost pressure.

[0006] Lithium disilicate-based LAS (Lithium Alkyl Silicate) glass: Renowned for its high toughness and high flexural strength, its interwoven rod-like crystal structure effectively inhibits crack propagation, making it a mainstream material in dental restorations and other fields. To balance high light transmittance and high strength, its formulation typically requires a higher Li₂O content (often greater than 25 mol%). This not only exacerbates the problems of poor chemical corrosion resistance and poor water resistance, similar to those of lithium feldspar systems, but also further increases the material cost.

[0007] To improve the impact resistance of LAS glass-ceramics, the industry generally adopts a composite process of "crystallization + chemical strengthening". However, high lithium content substrates require Li... + -Na + Plasma exchange can easily lead to "poisoning" of the molten salt bath and accelerate the decline of the material's water resistance, posing challenges to the strengthening effect and long-term reliability.

[0008] 2. Spinel Glass-Ceramics: Performance Potential and Practical Fabrication Challenges

[0009] To overcome the performance and cost limitations of the LAS system, microcrystalline glass with magnesium aluminum spinel (MgAl2O4) as the main crystalline phase is considered an ideal alternative. Spinel crystals themselves possess ultra-high hardness, high modulus, excellent chemical stability, and a wide light transmittance range, theoretically enabling a better combination of hardness, toughness, and light transmittance.

[0010] However, its industrialization faces severe challenges. Existing technologies generally suffer from difficulty in controlling crystallization behavior: grain coarsening easily affects transparency, or the precipitation of impurity phases (such as cordierite) leads to substandard performance. Particularly critical is the introduction of Li to balance ion exchange capacity. + Na + Alkali metal ions can severely interfere with the crystallization kinetics of spinel, resulting in an insufficient proportion of the target crystalline phase.

[0011] Numerous existing studies also confirm these difficulties. For example:

[0012] Chinese patent application CN116409933B discloses a transparent spinel microcrystalline glass with a crystallinity of <40%, and all disclosed formulations contain TiO2 and Ti. 4+ This can cause the glass to yellow and its optical properties to deteriorate. Chinese patent application CN118164677B discloses a highly scratch-resistant spinel microcrystalline glass with a Li₂O content of 0-2 wt%. Due to the low Li₂O content, it cannot provide sufficient Li for ion exchange. + Therefore, it cannot effectively improve the impact resistance of the strengthened microcrystalline glass. Chinese patent applications CN118184148B, CN118184152B, CN118270985B, and CN119977336B disclose a glass composition that does not contain Li. + Spinel-based transparent microcrystalline glass suffers from the problem of excessively long ion exchange times (9-48 hours), hindering large-scale production. Chinese patent applications CN118754429A, CN118812163A, CN118754440A, and CN1194099415A disclose a spinel-based transparent microcrystalline glass with a crystallinity ≤55%, which fails to meet mechanical performance requirements. Chinese patent application CN111615500A discloses an ion-exchangeable transparent zinc spinel-spinel microcrystalline glass with high hardness and modulus; however, its embodiments reveal a maximum crystallinity of 52.5 wt%, still insufficient to meet mechanical performance requirements.

[0013] In summary, mainstream LAS glass-ceramic systems are limited by inherent defects such as high cost, poor intrinsic chemical resistance, and side effects of strengthening processes. Meanwhile, spinel glass-ceramics, which are theoretically superior, are constrained by multiple contradictions between controllable crystallization, optical transparency, ion exchange efficiency, and mechanical properties, none of which have been adequately resolved by current technologies. Summary of the Invention

[0014] Therefore, the purpose of this invention is to provide an innovative spinel microcrystalline glass and its preparation method. This technical solution, through unique component design, achieves high-density, nano-sized, and uniform precipitation of the spinel phase without relying on high-cost lithium resources to construct the main crystalline phase, obtaining an extremely high crystal ratio (>53wt%). This simultaneously achieves excellent intrinsic mechanical properties, high light transmittance, and stable chemical durability. Furthermore, by precisely controlling the type and content of alkali metal ions used for ion exchange, while ensuring efficient chemical strengthening potential and significantly improving impact resistance, the overall material cost is greatly reduced, ultimately providing a novel high-performance mechanical glass material that comprehensively surpasses existing LAS systems.

[0015] On one hand, this application provides a precursor glass for preparing spinel glass-ceramics, wherein the precursor glass contains SiO2, Al2O3, ZrO2, R'O and R2O, wherein:

[0016] R'O represents a divalent metal oxide, which includes MgO and ZnO.

[0017] R₂O represents an alkali metal oxide, including Li₂O.

[0018] Based on the sum of the molar percentages of all components in the precursor glass being 100 mol%,

[0019] The SiO2 content in the precursor glass is 35 mol% to 55 mol%.

[0020] The content of Al2O3 in the precursor glass is greater than 20 mol% and less than or equal to 30 mol%;

[0021] The ZrO2 content in the precursor glass is 2 mol% to 7 mol%.

[0022] The MgO content in the precursor glass is 3 mol% to 12 mol%.

[0023] The ZnO content in the precursor glass is 5 mol% to 16 mol%.

[0024] The content of Li2O in the precursor glass is 4 mol% to 10 mol%.

[0025] According to this application, the precursor glass of the present invention does not contain As2O3, As2O5 and nitrates.

[0026] According to this application, the precursor glass of the present invention does not contain TiO2.

[0027] In one embodiment, the Al2O3 and SiO2 of the precursor glass of the present invention satisfy the following relationship:

[0028] The [Al2O3] / [SiO2] ratio is between 0.4 and 0.85, more preferably between 0.5 and 0.7, wherein:

[0029] [Al2O3] represents the molar percentage content of Al2O3 in the precursor glass;

[0030] [SiO2] represents the molar percentage content of SiO2 in the precursor glass.

[0031] In one embodiment, the MgO, ZnO, and Al2O3 of the precursor glass of the present invention satisfy the following relationship:

[0032] The value of {[ZnO]+[MgO]} / [Al2O3] is between 0.4 and 0.9, and more preferably between 0.6 and 0.8, wherein:

[0033] [ZnO] represents the molar percentage content of ZnO in the precursor glass;

[0034] [MgO] represents the molar percentage content of MgO in the precursor glass;

[0035] [Al2O3] represents the molar percentage content of Al2O3 in the precursor glass.

[0036] In one embodiment, the R2O and Al2O3 of the precursor glass of the present invention satisfy the following relationship:

[0037] The value of [R2O] / [Al2O3] is between 0.2 and 0.45, and more preferably between 0.23 and 0.38, wherein:

[0038] [R2O] represents the molar percentage content of R2O in the precursor glass.

[0039] [Al2O3] represents the molar percentage content of Al2O3 in the precursor glass.

[0040] In one embodiment, the R'O and Al2O3 of the precursor glass of the present invention satisfy the following relationship:

[0041] The value of [R'O] / [Al2O3] is between 0.45 and 0.95, and more preferably between 0.62 and 0.83, wherein:

[0042] [R'O] represents the molar percentage content of R'O in the precursor glass.

[0043] [Al2O3] represents the molar percentage content of Al2O3 in the precursor glass.

[0044] In one embodiment, the content of SiO2 in the precursor glass of the present invention is 42 mol% to 52 mol%; the content of Al2O3 in the precursor glass of the present invention is 22 mol% to 28 mol%; the content of ZrO2 in the precursor glass of the present invention is 3 mol% to 6 mol%; the content of MgO in the precursor glass of the present invention is 3 mol% to 10 mol%; the content of ZnO in the precursor glass of the present invention is 5 mol% to 13 mol%; and the content of Li2O in the precursor glass of the present invention is 6.1 mol% to 9 mol%.

[0045] In one embodiment, the content of SiO2 in the precursor glass of the present invention is 44 mol% to 49 mol; the content of Al2O3 in the precursor glass of the present invention is 24 mol% to 27 mol; the content of ZrO2 in the precursor glass of the present invention is 3 mol% to 5 mol; the content of MgO in the precursor glass of the present invention is 5 mol% to 8 mol; the content of ZnO in the precursor glass of the present invention is 7 mol% to 10 mol; and the content of Li2O in the precursor glass of the present invention is 6.1 mol% to 8 mol.

[0046] In one embodiment, the R2O of the precursor glass of the present invention further comprises at least one of Na2O and K2O.

[0047] According to this application, the content of Na2O in the precursor glass of this invention is less than 2 mol.

[0048] In one embodiment, the content of K2O in the precursor glass of the present invention is 0-5 mol%, preferably 0-3 mol%, and more preferably 0-2 mol%.

[0049] In one embodiment, the precursor glass of the present invention further comprises a clarifying agent at a content of less than 0.3 mol%, wherein the clarifying agent is not As2O3, As2O5, or nitrates. Preferably, the clarifying agent is at least one selected from Na2SO4, NaCl, CeO2, Sb2O3, and SnO2.

[0050] In one embodiment, the R'O of the precursor glass of the present invention further comprises at least one selected from CaO, BaO, and SrO. The content of CaO in the precursor glass of the present invention is 0-5 mol%, preferably 0-3 mol%, more preferably 0-1 mol%. The content of BaO in the precursor glass of the present invention is 0-3 mol%, preferably 0-2 mol%, more preferably 0-1.5 mol%. The content of SrO in the precursor glass of the present invention is 0-3 mol%, preferably 0-2 mol%, more preferably 0-1.5 mol%.

[0051] In one embodiment, the precursor glass of the present invention further comprises one or more of a flux, a phase separation promoter, and a rare earth oxide, wherein the phase separation promoter is not TiO2.

[0052] The flux content in the precursor glass of the present invention is 0-3 mol%, preferably 0-2.5 mol%, more preferably 0-2 mol%. The phase separation promoter content in the precursor glass of the present invention is 0-2 mol%, preferably 0-1.5 mol%, more preferably 0-1 mol%, and the rare earth oxide content in the precursor glass of the present invention is 0-1 mol.

[0053] Preferably, the flux is B2O3, the phase separation promoter is P2O5, and the rare earth oxide is Y2O3 and / or La2O3. The content of Y2O3 in the precursor glass of the present invention is 0-1 mol%, and the content of La2O3 in the precursor glass of the present invention is 0-1 mol%.

[0054] According to this application, the precursor glass of the present invention has a Tg of 650~750℃.

[0055] On the other hand, this application provides a spinel glass-ceramic, which comprises crystal family 1 and crystal family 2, wherein crystal family 1 comprises crystals having the following structural formula:

[0056] (Zn x Mg 1-x-y Al 2-2y (Al) 2y Mg y O4

[0057] in:

[0058] 0≤x≤1;

[0059] 0≤y≤1; and

[0060] 0≤x+y≤1;

[0061] Crystal group 2 includes zirconium oxide;

[0062] The microcrystalline glass is transparent in the visible light range.

[0063] In one embodiment, the crystal family 1 includes one or more of ZnAl2O4, MgAl2O4 and (Zn,Mg)Al2O4.

[0064] According to this application, the crystal group 2 of the spinel microcrystalline glass of the present invention comprises multiple crystal phases with zirconium oxide as the main component, such as monoclinic zirconium oxide, tetragonal zirconium oxide, and cubic zirconium oxide. Therefore, in one embodiment, the zirconium oxide included in the crystal group 2 is one or more of monoclinic zirconium oxide, tetragonal zirconium oxide, and cubic zirconium oxide.

[0065] In one embodiment, the microcrystalline glass of the present invention further includes crystal group 3, which includes one or more of spodumene, nepheline, lithium silicate, quartz and their solid solutions.

[0066] In one embodiment, the content of crystal group 1 in the microcrystalline glass of the present invention is 45wt% to 70wt%, and the content of crystal group 2 in the microcrystalline glass of the present invention is 8wt% to 15wt%.

[0067] According to this application, the microcrystalline glass of the present invention exhibits a total crystallinity of at least 53 wt%, preferably at least 60 wt%, wherein the total crystallinity is the sum of the crystal contents of all crystalline phases in the microcrystalline glass.

[0068] In one embodiment, crystal family 1 has an average crystal size of less than 10 nm, crystal family 2 has an average crystal size of less than 8 nm, and the average crystal size of crystal family 1 is greater than the average crystal size of crystal family 2.

[0069] In one embodiment, the crystals of all crystalline phases in the microcrystalline glass of the present invention are combined to form composite particles with an average particle size of 20-50 nm. Preferably, the average particle size of the composite particles is 20-40 nm, more preferably 25-35 nm.

[0070] According to this application, at a wavelength of 550 nm, the light transmittance of the microcrystalline glass of the present invention is greater than 85%, preferably greater than 89%, and more preferably greater than 90%.

[0071] In one embodiment, the elastic modulus of the microcrystalline glass of the present invention is greater than 105 GPa, preferably greater than 110 GPa, and even more preferably greater than 120 GPa.

[0072] In one embodiment, the Vickers hardness of the microcrystalline glass of the present invention is greater than 760 kgf / mm². 2 .

[0073] In one embodiment, the microcrystalline glass of the present invention contains the following components, based on a total molar percentage of 100 mol% of all components in the microcrystalline glass:

[0074] SiO2: 35 mol%~55 mol%, preferably 42 mol%~52 mol%, more preferably 44 mol%~49 mol%;

[0075] CaO: 0~5 mol%, preferably 0~3 mol%, more preferably 0~1 mol%;

[0076] Al2O3: greater than 20 mol% and less than or equal to 30 mol%, preferably 22 mol%~28 mol%, more preferably 24 mol%~27 mol%;

[0077] B2O3: 0~3 mol%, preferably 0~2.5 mol%, more preferably 0~2 mol%;

[0078] P2O5: 0~2 mol%, preferably 0~1.5 mol%, more preferably 0~1 mol%;

[0079] ZrO2: 2 mol%~7 mol%, preferably 3 mol%~6 mol%, more preferably 3 mol%~5 mol%;

[0080] MgO: 3 mol%~12 mol%, preferably 3 mol%~10 mol%, more preferably 5 mol%~8 mol%;

[0081] ZnO: 5 mol%~16 mol%, preferably 5 mol%~13 mol%, more preferably 7 mol%~10 mol%;

[0082] BaO: 0~3 mol%, preferably 0~2 mol%, more preferably 0~1.5 mol%;

[0083] Na₂O: ≥0 and <2 mol%;

[0084] Li₂O: 4 mol%~10 mol%, preferably 6.1 mol%~9 mol%, more preferably 6.1 mol%~8 mol%;

[0085] K2O: 0~5 mol%, preferably 0~3 mol%, more preferably 0~2 mol%;

[0086] Y₂O₃: 0~1 mol%;

[0087] La2O3: 0~1 mol%;

[0088] SrO: 0~3 mol%;

[0089] Clarifying agent: 0~0.3 mol%;

[0090] The clarifying agent is at least one selected from SnO2, NaCl, CeO2, and Sb2O3, and

[0091] The composition of the microcrystalline glass satisfies the following relationship:

[0092] The [Al2O3] / [SiO2] ratio is between 0.4 and 0.85, and more preferably between 0.5 and 0.7.

[0093] The value of {[ZnO]+[MgO]} / [Al2O3] is between 0.4 and 0.9, and more preferably between 0.6 and 0.8.

[0094] The value of [R2O] / [Al2O3] is between 0.2 and 0.45, and more preferably between 0.23 and 0.38.

[0095] The value of [R'O] / [Al2O3] is between 0.45 and 0.95, and more preferably between 0.62 and 0.83.

[0096] in:

[0097] [Al2O3] indicates the molar percentage content of Al2O3 in the glass-ceramic.

[0098] [SiO2] represents the molar percentage content of SiO2 in the glass-ceramic.

[0099] [ZnO] indicates the molar percentage content of ZnO in the glass-ceramic;

[0100] [MgO] indicates the molar percentage content of MgO in the glass-ceramic.

[0101] R2O can be Li2O, Na2O, or K2O, and [R2O] represents the molar percentage content of R2O in the glass-ceramic.

[0102] R'O can be MgO, ZnO, CaO, BaO, or SrO, and [R'O] represents the molar percentage content of R'O in the glass-ceramic.

[0103] In one embodiment, the microcrystalline glass of the present invention is free from As2O3, As2O5, nitrates and TiO2.

[0104] Accordingly, this application also provides a method for preparing the microcrystalline glass of the present invention, the method comprising the following steps:

[0105] 1) Preparation of precursor glass

[0106] The corresponding raw materials of each component contained in the target precursor glass are fully mixed in proportion, melted at 1550~1650℃ for 2~15h and shaped to obtain the target precursor glass.

[0107] 2) Heat treatment

[0108] The obtained target precursor glass was subjected to nucleation and crystallization treatments in sequence.

[0109] 3) Cooling

[0110] After heat treatment, the crystallized precursor glass is cooled to room temperature to obtain the desired glass-ceramic.

[0111] The nucleation temperature is lower than the crystallization temperature, and

[0112] The heat treatment step shall be performed at least once.

[0113] In one embodiment, in the heat treatment step 2) of the microcrystalline glass preparation method of the present invention, the nucleation temperature used for nucleation is 680-780℃ and the nucleation time is 240-600 min; the crystallization temperature used for crystallization is 740-860℃ and the crystallization time is 50-120 min.

[0114] In one embodiment, during the heat treatment process of the method for preparing the microcrystalline glass of the present invention, according to P = Calculate 7200≤P≤18000, where:

[0115] P represents the Larson-Miller parameter;

[0116] T is the heat treatment temperature expressed in Kelvin;

[0117] t represents the heat treatment time in hours.

[0118] In one embodiment, in the precursor glass preparation step of the method for preparing microcrystalline glass of the present invention, before heat treatment, the formed glass is annealed, preferably fine annealed. For example, the formed glass can be placed in a muffle furnace at 650°C for a period of time for fine annealing, thereby removing the stress present inside the glass.

[0119] In one embodiment, in the method for preparing the microcrystalline glass of the present invention, after heat treatment, the glass is sequentially sliced ​​and polished.

[0120] In one embodiment, during the nucleation stage of heat treatment step 2) of the method for preparing microcrystalline glass of the present invention, the target precursor glass is heated from the initial temperature to the nucleation temperature at a first heating rate.

[0121] In the crystallization stage of heat treatment step 2) of the preparation method of microcrystalline glass of the present invention, the nucleated target precursor glass is heated from the nucleation temperature to the crystallization temperature at a second heating rate.

[0122] In the cooling step 3) of the preparation method of the microcrystalline glass of the present invention, the crystallized target precursor glass is cooled from the crystallization temperature to room temperature by natural cooling or by cooling the crystallized target precursor glass from the crystallization temperature to room temperature at a certain cooling rate.

[0123] The first heating rate may be the same as or different from the second heating rate.

[0124] In one embodiment, the first heating rate is 1~20℃ / min, and the second heating rate is 1~15℃ / min.

[0125] In cooling step 3), the crystallized target precursor glass is cooled from the crystallization temperature to room temperature at a certain cooling rate, and the cooling rate is 1~10℃ / min.

[0126] In one embodiment, the method for preparing the microcrystalline glass of the present invention further includes the following steps:

[0127] Following step 1), the resulting target precursor glass is subjected to annealing treatment, and / or

[0128] After step 2), the crystallized precursor glass is annealed.

[0129] On the other hand, this application provides a chemically strengthened microcrystalline glass, which is obtained by chemically strengthening the microcrystalline glass of the present invention through ion exchange, using KNO3 and / or NaNO3 as the salt bath.

[0130] Specifically, the present invention provides a chemically strengthened glass-ceramic, the chemically strengthened glass-ceramic comprising a glass-ceramic matrix and a compressive stress layer formed on the surface of the matrix through ion exchange chemical strengthening, wherein:

[0131] The microcrystalline glass substrate comprises crystal family 1 and crystal family 2, wherein crystal family 1 comprises crystals having the following structural formula:

[0132] (Zn x Mg 1-x-y Al 2-2y (Al) 2y Mg y O4

[0133] in:

[0134] 0≤x≤1;

[0135] 0≤y≤1; and

[0136] 0≤x+y≤1;

[0137] Crystal group 2 includes zirconium oxide;

[0138] The compressive stress layer has a CTLD_saf value of 15000~70000 MPa.

[0139] In one embodiment, in the chemically strengthened glass-ceramic of the present invention, the crystal group 1 contained in the glass-ceramic matrix includes one or more of ZnAl2O4, MgAl2O4 and (Zn,Mg)Al2O4.

[0140] As previously stated, the spinel microcrystalline glass of the present invention comprises crystal group 2, including monoclinic zirconium oxide, tetragonal zirconium oxide, cubic zirconium oxide, and other crystalline phases with zirconium oxide as the main component. Therefore, in one embodiment of the chemically strengthened microcrystalline glass of the present invention, the zirconium oxide included in crystal group 2 is one or more of monoclinic zirconium oxide, tetragonal zirconium oxide, and cubic zirconium oxide.

[0141] Any chemical strengthening method known in the art can be used in this invention. In the examples below, the following method is used for chemical strengthening:

[0142] The microcrystalline glass substrate (i.e., the microcrystalline glass of the present invention) is placed in the salt bath at 400~450℃ and kept for 150~300 min.

[0143] In one embodiment, the salt bath used in this invention is 100 wt% NaNO3 or a composite salt bath containing 20-70 wt% KNO3 and 80-30 wt% NaNO3.

[0144] In one embodiment, the microcrystalline glass is polished before chemical strengthening.

[0145] In a preferred embodiment, the CTLD_saf of the chemically strengthened microcrystalline glass of the present invention is 30,000~70,000 MPa, more preferably 45,000~65,000 MPa.

[0146] In a preferred embodiment, the chemically strengthened microcrystalline glass of the present invention further possesses at least one of the following mechanical properties:

[0147] DOL0: 75~110μm;

[0148] CT-CV: 55~140 MPa;

[0149] CS: 100~470 MPa;

[0150] CS50: 35~170 MPa;

[0151] CT-AV: 25~110 MPa;

[0152] 4PB flexural strength: 510~840 MPa.

[0153] In another preferred embodiment, the chemically strengthened microcrystalline glass of the present invention also possesses at least one of the following impact resistance properties:

[0154] The drop height of a 32g steel ball at nine o'clock is 600~1100 mm.

[0155] Drop height of 180-grit sandpaper: 700~1700 mm;

[0156] Drop height of 80-grit sandpaper: 600~1300 mm.

[0157] In one embodiment, the glass-ceramic matrix of the chemically strengthened glass-ceramic of the present invention exhibits a total crystallinity of at least 53 wt%, preferably at least 60 wt%.

[0158] In one embodiment, the crystals of all crystalline phases in the microcrystalline matrix of the chemically strengthened microcrystalline glass of the present invention are combined together to form composite particles with an average particle size of 15-50 nm.

[0159] In one embodiment, the glass-ceramic matrix of the chemically strengthened glass-ceramic of the present invention contains crystal group 1 having an average crystal size of less than 10 nm, crystal group 2 having an average crystal size of less than 8 nm, and the average crystal size of crystal group 1 being greater than the average crystal size of crystal group 2.

[0160] In this application, the microcrystalline glass of the present invention is used as the microcrystalline glass matrix of the chemically strengthened microcrystalline glass of the present invention. Therefore, the composition of the microcrystalline glass matrix is ​​exactly the same as the composition of the microcrystalline glass of the present invention, and will not be described again here.

[0161] In one embodiment, the microcrystalline glass matrix contains the following components, based on a total molar percentage of 100 mol% for all its components:

[0162] SiO2: 35 mol%~55 mol%;

[0163] CaO: 0~5 mol%;

[0164] Al2O3: greater than 20 mol% and less than or equal to 30 mol%;

[0165] B2O3: 0~3 mol%;

[0166] P2O5: 0~2 mol%;

[0167] ZrO2: 2 mol%~7 mol%;

[0168] MgO: 3 mol%~12 mol%;

[0169] ZnO: 5 mol%~16 mol%;

[0170] BaO: 0~3 mol%;

[0171] Na₂O: ≥0 and <2 mol%;

[0172] Li₂O: 4 mol%~10 mol%;

[0173] K2O: 0~5 mol%;

[0174] Y₂O₃: 0~1 mol%;

[0175] La2O3: 0~1 mol%;

[0176] SrO: 0~3 mol%;

[0177] Clarifying agent: 0~0.3 mol%;

[0178] The clarifying agent is at least one selected from SnO2, NaCl, CeO2, and Sb2O3, and

[0179] The composition of the microcrystalline glass matrix satisfies the following relationship:

[0180] The [Al2O3] / [SiO2] ratio is between 0.4 and 0.85.

[0181] The value of {[ZnO]+[MgO]} / [Al2O3] is between 0.4 and 0.9.

[0182] The ratio of [R₂O] to [Al₂O₃] is between 0.2 and 0.45.

[0183] [R'O] / [Al2O3] is a value between 0.45 and 0.95, where:

[0184] [Al2O3] indicates the molar percentage content of Al2O3 in the microcrystalline glass matrix;

[0185] [SiO2] represents the molar percentage content of SiO2 in the glass-ceramic matrix;

[0186] [ZnO] indicates the molar percentage content of ZnO in the glass-ceramic matrix;

[0187] [MgO] represents the molar percentage content of MgO in the microcrystalline glass matrix;

[0188] R2O can be Li2O, Na2O, or K2O, and [R2O] represents the molar percentage content of R2O in the microcrystalline glass matrix.

[0189] R'O can be MgO, ZnO, CaO, BaO, or SrO, and [R'O] represents the molar percentage content of R'O in the microcrystalline glass matrix.

[0190] On the other hand, this application provides a portable electronic device comprising the chemically strengthened microcrystalline glass of the present invention, such portable electronic devices may include, but are not limited to, mobile phones, tablets and watches.

[0191] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0192] 1) High crystallinity and high elastic modulus and hardness

[0193] Spinel crystals differ significantly in refractive index from glass. By synergistically controlling the composition and crystallization process, the growth and uniformity of spinel grains are managed, ensuring good optical properties while maintaining high crystallinity, and achieving a total crystallinity of at least 53 wt%. Simultaneously, the elastic modulus is increased to above 105 GPa, and the Vickers hardness after crystallization is greater than 760 kgf / mm². 2 After strengthening, the Vickers hardness is greater than 790 kgf / mm. 2 .

[0194] 2) Excellent mechanical properties

[0195] The chemically strengthened microcrystalline glass of this invention has excellent mechanical properties: DOL0 is 75~110μm, CT-CV is 55~140MPa, CS is 100~470 MPa, CS50 is 35~170 MPa, CT-AV is 25~110 MPa, and 4PB flexural strength is 510~840MPa.

[0196] 3) Excellent optical properties

[0197] The precursor glass of this invention does not contain the conventional nucleating agent TiO2, thus avoiding the problems of reduced transmittance and excessive haze after glass crystallization caused by TiO2 coloring. At a wavelength of 550 nm, the light transmittance of the spinel microcrystalline glass obtained by heat treatment is greater than 85%, preferably greater than 89%, and more preferably greater than 90%.

[0198] 4) As2O3 and As2O5 were not used.

[0199] As₂O₃ and As₂O₅ are toxic and harmful substances, especially as₂O₃ and As₂O₅, which are prohibited substances. The precursor glass of this invention does not contain these substances, thus avoiding the harm they could cause to human health and the environment. Furthermore, excessive or incomplete decomposition of As₂O₃ and As₂O₅ may leave residual bubbles, affecting glass uniformity; improper control of nitrate decomposition may lead to changes in the reducing atmosphere or the generation of nitrogen oxide pollution. This invention does not use these substances, eliminating their impact on the product and ensuring product quality.

[0200] 5) Excellent impact resistance

[0201] The chemically strengthened microcrystalline glass of this invention also has excellent impact resistance, with a CTLD_saf of 15000~70000Mpa, and a drop height of 600~1100mm for a 32g steel ball at nine points, a drop height of 700~1700mm for 180-grit sandpaper, and a drop height of 600~1300mm for 80-grit sandpaper. Attached Figure Description

[0202] Figure 1 The image shows the XRD pattern of the spinel glass-ceramic prepared in Example 1 of this application.

[0203] Figure 2 This is a scanning electron microscope (SEM) image of the spinel microcrystalline glass prepared in Example 1 of this application.

[0204] Figure 3 This is a normal distribution diagram of the composite particle size in the SEM image of the spinel microcrystalline glass prepared in Example 1 of this application.

[0205] Figure 4 This is a Vickers hardness test diagram of the spinel microcrystalline glass prepared in Example 1 of this application.

[0206] Figure 5 This is a compressive stress distribution diagram of the chemically strengthened microcrystalline glass prepared in Example 1 of this application, where: the vertical axis represents the magnitude of the compressive stress, in megapascals (MPa); the horizontal axis represents the depth from the glass surface to the interior, in micrometers.

[0207] Figure 6This is the spectral transmittance spectrum of the chemically strengthened microcrystalline glass sample prepared in Example 1 of this application.

[0208] Figure 7 This is a safety breakage verification diagram of the chemically strengthened microcrystalline glass sample prepared in Example 4 of this application. Detailed Implementation

[0209] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0210] This invention develops a highly crystalline transparent microcrystalline glass with spinel as the main crystalline phase through the design and optimization of glass formulation and heat treatment process. Since spinel crystals have a significantly different refractive index from glass, the growth and uniformity of spinel grains are controlled through the synergistic effect of various components and crystallization process, ensuring good optical performance while maintaining high crystallinity.

[0211] In practice, the inventors of this application have discovered that when the Li2O content is >6 mol% and the Na2O content is <2 mol%, microcrystalline glass can achieve high impact resistance after ion exchange through chemical strengthening.

[0212] Furthermore, the clarifying agent used in this application does not contain toxic or harmful substances such as As2O3, As2O5, and nitrates, thus avoiding the hazards caused by these substances. This invention uses ZrO2 as a single nucleating agent, instead of the conventional nucleating agent TiO2, which avoids the problems of reduced transmittance and excessive haze after glass crystallization caused by the coloring of TiO2.

[0213] In this application, the term "precursor glass" refers to glass that has not undergone nucleation or crystallization treatment, and is typically prepared by the following methods:

[0214] Various oxides (including silicon dioxide, aluminum oxide, lithium oxide, etc.) and their corresponding compounds (such as silicon dioxide, aluminum hydroxide, lithium carbonate, etc.) are uniformly mixed, melted at high temperature, and then shaped using one of the following forming methods: float method, overflow pull method, or calendering method.

[0215] After being formed by the molding process, the precursor glass can be processed into suitable dimensions for subsequent heat treatment processes.

[0216] The heat treatment process used in this application has a Larson-Miller parameter P that satisfies: 7200 ≤ P ≤ 18000, where: P = T represents the heat treatment temperature in Kelvin (K), and t represents the heat treatment time in hours (h). The heat treatment includes annealing of the precursor glass, nucleation to induce crystallization in the glass-ceramic, crystallization heat treatment, and optionally, a 3D hot bending process to shape the glass-ceramic. By controlling the LMP value throughout the entire thermal process within the aforementioned range, it is possible to ensure that the material achieves an excellent crystalline structure while maintaining good processability and final properties.

[0217] In this application, R2O represents alkali metal oxides, including Li2O, Na2O, K2O, and any combination thereof. For example, R2O can be Li2O; Li2O and Na2O; Li2O and K2O; Li2O, Na2O, and K2O, etc. Its exact meaning needs to be determined based on the specific scheme and context. R'O represents divalent metal oxides, including MgO, ZnO, CaO, BaO, SrO, and any combination thereof. For example, R'O can be MgO and ZnO; MgO, ZnO, and CaO; MgO, ZnO, and BaO; MgO, ZnO, and SrO; MgO, ZnO, CaO, and SrO; MgO, ZnO, CaO, BaO, and SrO, etc. Its exact meaning needs to be determined based on the specific scheme and context.

[0218] In this application, the term "nucleation" refers to the growth of tiny crystal nuclei from nucleating material in a precursor glass through heat treatment.

[0219] In this application, the term "crystallization" means growing a precursor glass into a certain crystal based on a crystal nucleus through heat treatment.

[0220] In this application, the term "crystal phase" refers to a single type of crystal precipitated in a glass-ceramic matrix, possessing a definite crystal structure and chemical composition. The term "crystal family" refers to a set of crystal phases that are systematically precipitated in a glass-ceramic matrix through specific composition design and heat treatment processes, exhibiting a clear correlation between crystal chemistry and structure, rather than the isolated existence of a single crystal phase. In this application, crystal family 1 refers to a crystal phase family with a structure similar to AB₂O₄ spinel, which includes crystals with the following structural formulas:

[0221] (Zn x Mg 1-x-y Al 2-2y (Al) 2y Mg y O4

[0222] Where: A can be Zn, Mg, ZnMg, or ZnMgAl, and B can be Al or AlMg.

[0223] In this application, the term "total crystallinity" or "crystallinity" refers to the sum of the crystal weight content of all crystalline phases in a glass-ceramic.

[0224] The sources of SiO2 are quartz sand; Al2O3 is derived from Al2O3 or Al(OH)3; MgO is derived from MgO, MgCO3, or Mg(OH)2; ZrO2 is derived from ZrO2; Na2O is derived from Na2CO3, NaNO3, or Na2SO4; Li2O is derived from Li2CO3 or LiNO3; ZnO is derived from ZnO; CaO is derived from CaCO3; B2O3 is derived from boric acid; P2O5 is derived from Al(PO3)3; BaO is derived from BaCO3 or Ba(NO3)2; K2O is derived from K2CO3 or KNO3; and SrO is derived from SrCO3 or Sr(NO3)2.

[0225] SiO2 is the most important network formant in the glass system of this invention. It forms [SiO4] tetrahedra connected by Si–O–Si bonds, constituting the basic three-dimensional network structure of the glass. The Si–O bond is a strongly polar covalent bond with high bond energy, which gives the SiO2-based glass system high mechanical strength, low coefficient of thermal expansion, and good chemical stability and dielectric properties. As the SiO2 content increases, the degree of glass network polymerization improves, and the structural stability and resistance to chemical corrosion of the glass are enhanced. However, when the SiO2 content is too high, the viscosity of the glass melt increases significantly, leading to higher melting temperature, increased difficulty in melt homogenization and clarification, and making it unfavorable for preparing precursor glasses with uniform composition and no bubbles. Furthermore, in Mg / Zn–Al–Si-based glass-ceramic systems, excessive SiO2 content can increase the stability of the glass network and weaken the rearrangement and enrichment capabilities of crystallizing elements such as Mg, Zn, and Al during heat treatment, thereby inhibiting the effective precipitation of spinel phases. Simultaneously, excessive SiO2 may also promote the formation of quartz or silicate impurities, thus reducing the material's optical transmittance. Therefore, the SiO2 content in this invention needs to be controlled within an appropriate range to balance the glass's meltability, structural stability, and subsequent crystallization behavior.

[0226] Al₂O₃ is an important network intermediate in the glass system of this invention, and its coordination state in the glass is closely related to the type and content of charge-compensating ions in the system. Let R₂O represent alkali metal oxides and R'O represent divalent metal oxides. When {[R₂O] + [R'O]} / [Al₂O₃] ≥ 1 (molar percentage), Al³⁺ + Mainly composed of [AlO4] -Tetrahedral structures participate in the construction of the glass network and form stable Al–O–Si or Al–O–(Zn / Mg) bridging structures through charge compensation; when {[R2O]+[R'O]} / [Al2O3]<1, some Al³ + Insufficient charge compensation results in Al₂O₃ existing as [AlO₆] octahedrons in the gaps of the glass network, thus altering the local structural characteristics of the glass. The introduction of appropriate amounts of Al₂O₃ can increase the degree of cross-linking in the glass network, reduce the spontaneous crystallization tendency of the precursor glass during melting and cooling, and significantly improve the overall properties of the glass, including chemical stability, thermal stability, mechanical strength, hardness, and refractive index. Compared to [SiO₄] tetrahedra, [AlO₄]... - The tetrahedron has a larger effective size, and its introduction can expand the ion migration channels in the glass network without significantly disrupting the network continuity. This is beneficial for the diffusion and migration of alkali metal ions, and to a certain extent, improves the effective depth and stress accumulation capacity of subsequent ion exchange processes. Meanwhile, Al2O3, as a necessary component of the (Zn,Mg)Al2O4 spinel phase, has a decisive influence on the crystallization behavior of glass-ceramics. Under the condition of maintaining an appropriate {[ZnO]+[MgO]} / [Al2O3] ratio, moderately increasing the Al2O3 content is beneficial for providing sufficient crystallization sites, promoting the precipitation of the spinel phase, and increasing the crystal volume fraction. However, when the Al2O3 content is too high and charge compensation is insufficient, the melt viscosity increases significantly, making glass melting more difficult, and may induce structural instability or impurity phase formation, which is not conducive to obtaining stable transparent glass-ceramics.

[0227] MgO and ZnO are important divalent metal oxides in the glass system of this invention. They possess both network modification properties in the glass structure and, under specific conditions, can participate in the local construction of the glass network as network intermediates. Appropriate introduction of MgO and ZnO can contribute to [AlO4]... - The tetrahedron provides effective charge compensation, causing most of the Al₂O₃ in the system to be in the form of [AlO₄]. - The tetrahedral form exists stably and combines with the silicon-oxygen network through Al–O–Si and Al–O–(Zn / Mg) bridging structures, thereby improving the cross-linking degree and structural density of the glass network. Mg² + and Zn² +Both MgO and ZnO are divalent cations with moderate field strength, and the metal-oxygen bond strength they form with oxygen is relatively high. Compared with alkali metal oxides or large-radius, low-field-strength alkaline earth metal oxides, the introduction of appropriate amounts of MgO and ZnO is beneficial to improving the elastic modulus and structural rigidity of the precursor glass, thereby improving the mechanical properties of the glass. Simultaneously, MgO and ZnO have relatively high intrinsic refractive indices, and their introduction can increase the overall refractive index of the precursor glass without significantly reducing its transparency, narrowing the refractive index difference between the glass matrix and the subsequently precipitated (Zn,Mg)Al2O4 spinel phase, which is beneficial for obtaining transparent microcrystalline glass with higher optical homogeneity. During heat treatment, ZnO exhibits high structural activity in the glass system of this invention, and can synergistically act with nucleating components such as ZrO2 to promote the formation of a sufficient number and uniformly distributed nucleation sites, providing favorable conditions for the precipitation of the (Zn,Mg)Al2O4 spinel phase; at the same time, since the spinel phase preferentially consumes Zn²⁺... + Mg² + and Al³ + This, to a certain extent, inhibits the precipitation of quartz phase and Li₂O-containing silicate impurities. However, when the ZnO content is too high, the Zn²⁺ in the melt… + The enhanced structural activity and diffusion capacity of the precursor glass make it prone to uncontrolled premature crystallization during melting or cooling, leading to devitrification or compositional inhomogeneity. To address this, this invention introduces the precursor glass in combination with MgO. This maintains the required divalent metal content for the spinel crystal phase while synergistically controlling the glass's melt stability and crystallization tendency. This allows the precursor glass to achieve a high crystal volume fraction during subsequent heat treatment while maintaining good meltability.

[0228] SrO and BaO are divalent alkaline earth metal oxides with large radii and low electric field strength, and they mainly exhibit network exosome characteristics in glass structures. Appropriate introduction of SrO or BaO can effectively reduce melt viscosity and liquidus temperature by increasing the amount of non-bridging oxygen and decreasing the degree of polymerization in the glass network, thereby improving the melting, refining, and casting properties of precursor glasses.

[0229] Due to Sr² + and Ba² + [AlO4] - Tetrahedrons have relatively weak charge compensation capabilities and are difficult to participate in the construction of Al–O–(Zn / Mg) bridging structures. Excessive introduction of SrO or BaO will "preempt" some of the AlO4- bridging. - The charge-compensating niche alters the structural role of Zn, Zn² +It is easier for the glass to shift to the [ZnO6] modified state rather than the [ZnO4] bridging state, thereby weakening the short-range ordered structure in the glass that is conducive to the formation of the spinel phase, reducing the nucleation density and final crystal volume fraction of the spinel phase. Therefore, in this invention, SrO and BaO are mainly used as components for regulating melt properties and processing window. Their content needs to be controlled at a low level, and their ratio with MgO, ZnO and Al2O3 should be synergistically optimized to ensure good processability of the precursor glass while avoiding adverse effects on subsequent crystallization behavior and optical properties.

[0230] ZrO2 is one of the key nucleating components in the glass system of this invention. 4+ In silicate glasses, it usually exists in a highly coordinated state. As a high-field-strength cation, the surrounding coordinated oxygen has a strong polarization ability, making [ZrO]... x (x≥6) The structural units exhibit obvious network intermediate characteristics in the glass and are preferentially distributed in the local high-energy regions of the glass network, thereby improving the thermal stability of the glass structure to a certain extent.

[0231] During the subsequent nucleation-crystallization heat treatment, the ZrO2 component readily accumulates locally within the glass network, forming nanoscale Zr-rich regions or microregions. These regions significantly lower the nucleation energy barrier of the spinel phase and preferentially adsorb Zn²⁺ as heterogeneous nucleation centers. + Mg² + and Al³ + The crystallizing ions induce the formation of ordered (Zn,Mg)Al2O4 spinel nuclei around them. Thus, in the system of this invention, ZrO2 mainly promotes the uniform precipitation and fine crystallization of the spinel phase by increasing the nucleation density rather than directly participating in the composition of the main crystal phase.

[0232] However, due to the limited solubility of ZrO2 in silicate glass, excessively high ZrO2 content can lead to decreased melt homogeneity during melting, increasing melting difficulty, and potentially causing the precipitation of non-target crystalline phases or abnormal crystal morphology during heat treatment. This is detrimental to obtaining transparent microcrystalline glass with stable structure and optical properties. Therefore, the ZrO2 content in this invention needs to be controlled within a reasonable range to balance the melting stability of the glass and the crystallization nucleation efficiency.

[0233] Li₂O and Na₂O are important monovalent alkali metal oxides in the spinel microcrystalline glass system of this invention. They mainly play a network modification role in the glass structure, and under certain conditions, they also act as [AlO₄] compounds. -The tetrahedral charge compensation function. Appropriate introduction of Li₂O and Na₂O can effectively reduce the melt viscosity of the precursor glass by introducing non-bridging oxygen and reducing the degree of polymerization of the glass network. This promotes complete dissolution of raw materials, melt homogenization, and bubble removal, which is beneficial for preparing precursor glasses with uniform composition and stable structure. Furthermore, Li₂O and Na₂O provide a necessary source of migratable alkali metal ions for subsequent ion exchange strengthening processes. + The ions have small ionic radii and high migration capabilities, which are beneficial for deepening the exchange layer during ion exchange; Na + Ions then react with external large-radius alkali metal ions (such as K+). + When ion exchange occurs, it is more conducive to forming higher residual compressive stress on the glass surface. By reasonably controlling the total content and ratio of Li2O and Na2O, microcrystalline glass can obtain higher surface compressive stress and a reasonably distributed stress gradient after ion exchange, thereby significantly improving the impact resistance and scratch resistance of strengthened microcrystalline glass. However, when the content of Li2O or Na2O is too high, on the one hand, it will significantly increase the proportion of non-bridging oxygen in the glass network, weaken the structural stability of the glass network, and make the precursor glass prone to crystallization devitrification during melting, refining or annealing; on the other hand, excessive alkali metal ions will compete with crystallizing components such as Al2O3 and SiO2 for rearrangement during heat treatment, easily forming quartz solid solution, spodumene or other alkali metal silicate impurity crystalline phases, thereby reducing the crystallization controllability and optical transmittance of microcrystalline glass. Therefore, in this invention, the amount of Li2O and Na2O introduced needs to be optimized in synergy with crystallization-related components such as Al2O3, ZnO, and MgO, while ensuring good melting performance and ion exchange strengthening effect of the precursor glass, so as to achieve preferential precipitation of spinel crystal phase during heat treatment and obtain transparent microcrystalline glass with stable performance.

[0234] [Al2O3] / [SiO2]:

[0235] In silicate network structures, SiO2 is a very important glass network-forming oxide, and each silicon atom (SiO2) is a key component. 4+ It forms a [SiO4] tetrahedron with four oxygen atoms, which are connected to form a three-dimensional network through bridging oxygen atoms, and Si 4+ With O 2-The electrostatic balance of each Si-O bond is achieved by the electrostatic bond strength ESB(Si-O) = 4 / 4 = 1, which balances the -2 valence of the oxygen ion, thus eliminating the need for additional charge balancing. Al₂O₃, as an intermediate oxide in the glass network, exists in two coordination modes: [AlO₆] and [AlO₄]. [AlO₄] can directly replace [SiO₄], participating in the construction of the glass network as a network-forming oxide. Although both [AlO₄] and [SiO₄] can serve as network-forming agents in silicate glasses, the difference in charge compensation before coordination leads to significant variations in their proportions within the silicate glass, even though both tetrahedra can function as part of the network framework. Therefore, the [Al₂O₃] / [SiO₂] ratio effectively describes the changes in the stability, viscosity, chemical stability, and crystallization behavior of the glass network structure. Through extensive experimental research, we found that when the [Al2O3] / [SiO2] ratio is between 0.4 and 0.85, and further optimized to be between 0.5 and 0.7, the glass network structure exhibits good stability and excellent crystallization behavior.

[0236] [R2O] / [Al2O3] and [R'O] / [Al2O3]:

[0237] In silicate network structures, to ensure the stability of the glass network structure, an appropriate amount of [AlO4] tetrahedra is needed to enter the glass network structure. Considering the charge balance issue, since Al... 3+ It carries 3 positive charges, slightly lower than Si. 4+ AlO4 contains four positive charges, so when forming a 4-coordinate system, we need to introduce additional monovalent or divalent cations to provide extra positive charges to compensate for the negative charge centers of AlO4. The electrostatic bond strength of each Al-O bond is ESB(Al-O) = 3 / 4 = 0.75. Since the ESB of the Al-O bond is lower than that of the Si-O bond, we need additional positive charges to compensate for the negative charge of AlO4, thereby enhancing the stability of the glass network structure. Therefore, we use [R2O] / [Al2O3] and [R'O] / [Al2O3] to describe the compensation effect of monovalent and divalent cations on the negative charge of AlO4. Through extensive experimental research, we found that when the ratio of [R2O] / [Al2O3] is between 0.2 and 0.45, and further preferably between 0.23 and 0.38; and when the ratio of [R'O] / [Al2O3] is between 0.45 and 0.95, and further preferably between 0.62 and 0.83, the inclusion of [AlO4] tetrahedra in the glass network after charge compensation can significantly improve the stability of the glass network structure.

[0238] {[ZnO]+[MgO]} / [Al2O3]:

[0239] In divalent metal oxides, ZnO and MgO, as components of the (Zn,Mg)Al2O4 spinel phase, have a decisive influence on the crystallization behavior of glass-ceramics. While maintaining an appropriate {[ZnO]+[MgO]} / [Al2O3] ratio, moderately increasing the Al2O3 content is beneficial for providing sufficient crystallization sites, promoting the precipitation of the spinel phase, and increasing the crystal content. A {[ZnO]+[MgO]} / [Al2O3] ratio between 0.4 and 0.9, more preferably between 0.6 and 0.8, allows the charge-compensated [AlO4] tetrahedra to enter the glass network, resulting in good crystallization behavior in the glass.

[0240] The molar percentage content of SiO2 used in this application is generally 35 mol% to 55 mol%, preferably 42 mol% to 52 mol%, and more preferably 44 mol% to 49 mol%. For example, the molar percentage content of SiO2 can be 35 mol%, 36 mol%, 37 mol%, 38 mol%, 39 mol%, 40 mol%, 41 mol%, 42 mol%, 43 mol%, 44 mol%, 45 mol%, 46 mol%, 47 mol%, 48 mol%, 49 mol%, 50 mol%, 51 mol%, 52 mol%, 53 mol%, 54 mol%, 55 mol%, or any two of the above values ​​forming any one of the ranges.

[0241] The molar percentage content of Al2O3 used in this application is generally 20 mol% < Al2O3 ≤ 30 mol%, preferably 22 mol% to 28 mol%, and more preferably 24 mol% to 27 mol%. For example, the molar percentage content of Al2O3 can be 20.5 mol%, 21 mol%, 22 mol%, 23 mol%, 24 mol%, 25 mol%, 26 mol%, 27 mol%, 28 mol%, 29 mol%, 30 mol%, or any value within the range of any two of the above values.

[0242] The molar percentage content of ZrO2 used in this application is generally 2 mol% ≤ ZrO2 ≤ 7 mol%, preferably 3 mol% to 6 mol%, and more preferably 3 mol% to 5 mol%. For example, the molar percentage content of ZrO2 can be 2 mol%, 3 mol%, 4 mol%, 5 mol%, 6 mol%, 7 mol%, or any value within the range of any two of the above values.

[0243] The molar percentage content of MgO used in this application is generally 3mol%≤MgO≤12mol%, preferably 3mol%~10mol%, and more preferably 5mol%~8mol%. For example, the molar percentage content of MgO can be 3mol%, 4mol%, 5mol%, 6mol%, 7mol%, 8mol%, 9mol%, 10mol%, 11mol%, 12mol%, and any value within the range of any two of the above values.

[0244] The molar percentage content of ZnO used in this application is generally 5 mol% ≤ ZnO ≤ 16 mol, preferably 5 mol% to 13 mol, and more preferably 7 mol% to 10 mol. For example, the molar percentage content of ZnO can be 5 mol%, 6 mol%, 7 mol%, 8 mol%, 9 mol%, 10 mol%, 11 mol%, 12 mol%, 13 mol%, 14 mol%, 15 mol%, 16 mol%, or any value within the range of any two of the above values.

[0245] The molar percentage content of Li2O used in this application is generally 4mol%≤Li2O≤10mol, preferably 6.1mol%~9mol, and more preferably 6.1mol%~8mol%. For example, the molar percentage content of Li2O can be 4mol%, 4.5mol%, 5mol%, 6mol%, 6.1mol%, 7mol%, 8mol%, 9mol%, 10mol%, or any value within the range of any two of the above values.

[0246] Besides Li₂O, this application may also use other alkali metal oxides, whose molar percentage content is generally 0-5 mol%. Preferably, the other alkali metal oxides are selected from Na₂O, K₂O, and combinations thereof. The molar percentage content of Na₂O used in this application is generally 0 ≤ Na₂O < 2 mol%. For example, the molar percentage content of Na₂O can be 0, 0.5 mol%, 1.0 mol%, 1.5 mol%, 1.9 mol%, or any value within the range of any two of the above values. The molar percentage content of K₂O used in this application is generally 0 ≤ K₂O ≤ 5 mol%, preferably 0-3 mol%, more preferably 0-5 mol%. For example, the molar percentage content of K₂O can be 0, 0.5 mol%, 1.0 mol%, 1.5 mol%, 2.0 mol%, 3.0 mol%, 4.0 mol%, 5.0 mol%, or any value within the range of any two of the above values.

[0247] Clarifying agents can promote the elimination of bubbles during high-temperature glass melting, which helps reduce the difficulty of glass melting and obtain high-quality, bubble-free, homogeneous parent glass. The clarifying agents that can be used in this application are at least one of Na₂SO₄, NaCl, CeO₂, SnO₂, and Sb₂O₃. The molar percentage content of the clarifying agent is generally 0 ≤ clarifying agent ≤ 0.3 mol%. For example, the molar percentage content of the clarifying agent can be 0, 0.1 mol%, 0.2 mol%, 0.3 mol%, or any value within the range of any two of the above values.

[0248] Besides MgO, this application may also use other alkaline earth metal oxides with a molar percentage content generally of 0-5 mol%. Preferably, the other alkaline earth metal oxides are selected from CaO, BaO, SrO, and combinations thereof. The molar percentage content of CaO used in this application is generally 0 ≤ CaO ≤ 5 mol%, preferably 0-3 mol%, and more preferably 0-1 mol%. For example, the molar percentage content of CaO can be 0, 1.0 mol%, 2.0 mol%, 3.0 mol%, 4.0 mol%, 5.0 mol%, or any value within the range of any two of the above values. The molar percentage content of BaO used in this application is generally 0 ≤ BaO ≤ 3 mol%, preferably 0-2 mol%, and more preferably 0-1.5 mol%. For example, the molar percentage content of BaO can be 0, 1.0 mol%, 2.0 mol%, 3.0 mol%, and any value within the range of any two of the above values. The molar percentage content of SrO used in this application is generally 0-3 mol%, preferably 0-2 mol%, and more preferably 0-1.5 mol%. For example, the molar percentage content of SrO can be 0, 1.0 mol%, 2.0 mol%, 3.0 mol%, or any value within the range of any two of the above values.

[0249] This application may also employ one or more of fluxes, phase separation promoters, and rare earth oxides.

[0250] This application uses B2O3 as a flux, and the molar percentage content of B2O3 is generally 0 ≤ B2O3 ≤ 3 mol%, preferably 0~2.5 mol%, and more preferably 0~2 mol%. For example, the molar percentage content of B2O3 can be 0, 1.0 mol%, 2.0 mol%, 3.0 mol%, or any value within the range of any two of the above values.

[0251] In the preparation of glass-ceramics, phase separation promoters can induce and promote microscopic and non-uniform structural phase separation (phase separation) in the initial stage of heat treatment of the original glass, forming micro-regions enriched with certain components. In this application, P2O5 is selected as the phase separation promoter. The molar percentage content of P2O5 is generally 0~2 mol%, preferably 0~1.5 mol%, more preferably 0~1 mol%.

[0252] The rare earth oxides used in this application are preferably Y2O3 and / or La2O3, with the molar percentage content of Y2O3 generally being 0~1 mol% and the molar percentage content of La2O3 generally being 0~1 mol%.

[0253] Example

[0254] Performance testing

[0255] 1. Young's modulus (or elastic modulus)

[0256] The Young's modulus of glass can be calculated using the following formulas (1) and (2):

[0257] E=(4G2-4GVT2ρ) / (G-VT2ρ) (1)

[0258] G=VS2ρ(2)

[0259] Where E is Young's modulus, Pa; G is shear modulus, Pa; VT is longitudinal wave velocity, m / s; VS is transverse wave velocity, m / s; and ρ is the density of the glass, g / cm³. 3 The longitudinal wave velocity VT and the transverse wave velocity VS can be obtained using ultrasonic testing. The density ρ of the glass can be determined according to GB / T7962.20. The test shall be conducted according to the method specified in 2010. The elastic modulus is limited to a range of 110~130, in GPa.

[0260] 2. Vickers hardness

[0261] The Vickers hardness tester used in this application was a Matsuzawa MMT-X7B-HRE microhardness tester from Japan. Test conditions: load 200 gf, loading time 15 s, and the validity of the indentation conformed to GB / T 37900-2019 "Test Methods for Hardness and Fracture Toughness of Ultrathin Glass - Small Load Vickers Hardness Indentation Method". At least three samples with the same sample number were tested, and measurements were taken at at least five different locations on the surface of each sample. The average of ten measurements was recorded as the Vickers hardness result of the test sample.

[0262] 3. CS, DOL and CT

[0263] After chemical strengthening, the compressive stress (CS), stress layer thickness (DOL), and central tensile stress (CT) of the glass surface were measured using the FSM-6000X and SLP-2000 glass surface stress meters manufactured by Orihara, Japan.

[0264] 4. CTLD

[0265] CTLD is defined as the average value of the total tensile stress inside the glass along its thickness. It can be considered as the compressive stress "borne" per unit thickness after the surface compressive stress is uniformly distributed throughout the entire glass thickness. CTLD not only reflects the average effect of surface compressive stress on the overall cross-section, but also, under static equilibrium conditions, the surface compressive stress and internal tensile stress must maintain overall mechanical equilibrium. Therefore, by integrating the compressive stress along the thickness direction and distributing it evenly over the total thickness, CTLD can be used to assess the distribution of internal stress in the glass. If we consider ultra-thin IOX glass as a two-dimensional infinitely large flat glass, its stress in the thickness direction is negligible. Therefore, its volumetric stress level is approximately the same as CTLD. Quantitative calculation using CTLD can more accurately reflect the glass's overall resistance to breakage under large external forces and high-speed strain (such as drop impacts), and this index is directly proportional to the integral of the compressive stress. Therefore, CTLD also characterizes the stress level stored in the glass after IOX treatment. A higher CTLD means greater energy storage, which, while enhancing strength, may also increase the risk of delayed failure or spontaneous breakage under environmental stress. In summary, CTLD is not only an important parameter for evaluating glass strength, but also a key indicator that cannot be ignored in safety design.

[0266]

[0267] In the formula, CTLD denoted as linear stress density, MPa; CT(t) represents the tensile stress at different locations along the thickness direction, MPa; t represents the thickness, mm.

[0268] For IOX LAS glass, the measurement of tensile stress is more accurate and can be simplified as follows:

[0269]

[0270] In the formula, CTLD t is the linear density of tensile stress, MPa; CT_AV is the average tensile stress, MPa; DOL_0 is the maximum depth of compressive stress, μm; t is the thickness, mm.

[0271] Different CTLD values ​​can be obtained by performing ion exchange at different temperatures and times. The maximum value of CTLD is CTLD_max, which represents the maximum energy that the glass can store.

[0272] Safety tests are conducted on glass with different processing conditions and different CTLD values. The safety of the glass can be determined based on the crack pattern. If the crack exhibits a non-fragile "starburst" fracture pattern, the glass can be considered safe. Under the premise that the glass is safe, the maximum CTLD is the maximum safety threshold CTLD_saf, which also represents the maximum safe energy storage value of the glass.

[0273] After chemical strengthening, non-destructive measurements are performed using a photoelasticity analyzer manufactured by Orihara in Japan. The CTLD value can be calculated according to the above formula. When conducting safety tests on the glass, the safety status of the glass can be determined, thus obtaining the CTLD_saf value.

[0274] 5. Bending strength

[0275] After stress testing is completed, mechanical testing is carried out. Before mechanical testing, the sample is inspected to ensure that the surface of the glass to be tested is free of defects such as scratches and chipping.

[0276] The four-point bending test equipment is a universal testing machine. The test bar has a diameter of 6 mm, an upper shaft distance of 20 mm, and a lower shaft distance of 40 mm. The pressing speed of the test bar is 10 mm / min. After the glass breaks, the bending strength data of each piece of glass is recorded.

[0277] 6. Nine-point ball impact test

[0278] The nine-point drop ball impact test equipment is a drop ball tester. The steel ball has a diameter of 20mm and a weight of 32g. The glass is subjected to nine single impacts at each height. The initial drop height of the steel ball is 50cm. If the glass sample does not break in nine tests at the same height, the drop height is increased by 10cm, and the next round of impact test is carried out until the glass breaks. The drop ball height data is recorded.

[0279] 7. Whole machine drop test

[0280] The drop test equipment is a drop test machine. The test glass sample is attached to the surface of the mobile phone mold. The total weight of the phone including the glass is 190g. 180-grit and 80-grit silicon carbide sandpaper are placed on a marble surface to simulate a rough surface. The initial drop height is 400mm, and the height is increased by 100mm each time. The sandpaper is replaced after every 3 drops and the experiment continues. When the drop height is below 600mm, free fall is used. When the drop height is above 600mm, a robotic arm is used to assist in controlled drop to ensure that the glass surface contacts the center of the sandpaper when it falls. The drop height is increased until the glass breaks. The drop height data is recorded.

[0281] Preparation Examples

[0282] 1. Preparation of spinel glass-ceramics

[0283] In the following embodiments, spinel glass-ceramics are prepared according to the following steps:

[0284] 1) Preparation of precursor glass

[0285] According to the designed target precursor glass formula, weigh the corresponding raw materials of each component, add them to the Y-type mixer and mix for 15 minutes, then add them to the glass furnace and melt at 1600℃ for 8 hours. After melting, the glass is formed by calendering. The formed glass is then placed in a muffle furnace at 650℃ for 3 hours for fine annealing to obtain the target precursor glass.

[0286] 2) Heat treatment

[0287] The target precursor glass was nucleated at a nucleation temperature of 680-780℃ for 240-600 min.

[0288] After nucleation, the nucleated precursor glass is crystallized at a crystallization temperature of 740-860℃ for 50-120 minutes.

[0289] 3) Cooling

[0290] After heat treatment, the crystallized precursor glass is cooled to room temperature to obtain the desired glass-ceramic.

[0291] The nucleation temperature is lower than the crystallization temperature.

[0292] The formulations and properties of the target precursor glasses for each embodiment are listed in Table 1 below. The heat treatment process conditions used in each embodiment and the crystal phase composition and properties of the prepared spinel microcrystalline glasses are listed in Table 2 below.

[0293] For comparison, the highest crystallinity example 28 of Corning Incorporated's Chinese application number CN 111615500 A was used as Comparative Example 1, the highest crystallinity example 4 of Guangming Incorporated's Chinese application number CN 116621455 B was used as Comparative Example 2, the highest crystallinity example 4 of Xinjing Incorporated's Chinese application number CN 118164680 A was used as Comparative Example 3, and Example 1 of Xinjing Incorporated's Chinese application number CN 118812163 A was used as Comparative Example 4. The glass formulations of Comparative Examples 1 to 4 are also shown in Table 1, and the heat treatment process conditions used in Comparative Examples 1 to 4 and the crystal phase composition and characteristics of the prepared spinel microcrystalline glass are also shown in Table 2.

[0294] Furthermore, those skilled in the art can easily determine the corresponding raw materials of each component contained in the target precursor glass. For example, it can be easily determined that the source of SiO2 is quartz sand; the source of Al2O3 is Al2O3, Al(OH)3, or Al(NO3)3; the source of MgO is MgO, MgCO, or Mg(OH)2; the source of ZrO2 is ZrO2; the source of Na2O is Na2CO3, NaNO3, or Na2SO4; the source of Li2O is Li2CO3 or LiNO3; the source of ZnO is ZnO, etc., which will not be listed here one by one.

[0295] Table 1

[0296]

[0297] Table 1 (Continued - 1)

[0298]

[0299] Table 1 (Continued - 2)

[0300]

[0301] Table 1 (Continued - 3)

[0302]

[0303] Table 2

[0304]

[0305] Table 2 (Continued - 1)

[0306]

[0307] Table 2 (continued - 2)

[0308]

[0309] Table 2 (continued - 3)

[0310]

[0311] Figure 1 The XRD pattern of the spinel glass-ceramic prepared in Example 1 is shown. As can be seen from the figure, the spinel glass-ceramic of the present invention comprises a first crystal group and a second crystal group, wherein the first crystal group includes ZnAl2O4, MgAl2O4, (Zn,Mg)Al2O4, and (Zn... 0.647 Mg 0.225 Al 0.128 (Al) 1.87 Mg 0.13 O4, the second group of crystals includes ZrO2.

[0312] Electron microscopy was performed on the spinel glass-ceramic prepared in Example 1, and the results are as follows: Figure 2 As shown in the figure, the crystals of crystal group 1 and crystal group 2 are combined to form composite particles, which are uniformly distributed in the glass matrix. Each composite particle is composed of several to dozens of crystals, with an average particle size between 15 and 50 nm.

[0313] Figure 3 The normal distribution diagram of the composite particle size in the SEM image of the spinel microcrystalline glass prepared in Example 1 is shown. According to the normal distribution diagram, the size of the composite particles is between 15 and 48 nm, with a minimum of 15.13 nm, a maximum of 47.26 nm, a median of 29.42 nm, and an average of 29.46 nm.

[0314] The spinel glass-ceramic prepared in Example 1 was also subjected to Vickers hardness testing, and the test results are shown in [Figure 1]. Figure 4 .

[0315] As shown in Table 2, compared with the comparative examples, the crystallinity and Vickers hardness of the spinel microcrystalline glasses in Examples 1-18 are significantly improved. The crystallinity of the spinel microcrystalline glasses in Examples 1-18 is all above 53 wt%, most are above 60 wt%, and the highest reaches 78.5 wt%, while the crystallinity of the comparative examples does not exceed 53 wt%. The Vickers hardness of the spinel microcrystalline glasses in Examples 1-18 is greater than 760 kgf / mm². 2 The elastic modulus is above 110 GPa.

[0316] 2. Preparation of chemically strengthened microcrystalline glass

[0317] The spinel glass-ceramics prepared in Examples 1-18 were polished and then chemically strengthened in a salt bath to obtain the corresponding chemically strengthened glass-ceramics. For convenience, the example numbers used in this section are consistent with those in section 1, Preparation of Spinel Glass-ceramics. For example, Example 1 in section 2, Preparation of Chemically Strengthened Glass-ceramics, corresponds to Example 1 in section 1, Preparation of Spinel Glass-ceramics. Other examples are similar and will not be listed individually. The salt bath, process conditions, and mechanical and impact resistance properties of the prepared chemically strengthened glass-ceramics are listed in Table 3 below.

[0318] Table 3

[0319]

[0320] Table 3 (Continued - 1)

[0321]

[0322] Table 3 (Continued - 2)

[0323]

[0324] Table 3 (Continued - 3)

[0325]

[0326] As shown in Table 3, the chemically strengthened microcrystalline glass of the present invention has excellent mechanical properties and impact resistance, especially its impact resistance. The drop height of a 32g steel ball at nine points, the drop height of a whole machine with 180-grit sandpaper, and the drop height of a whole machine with 80-grit sandpaper are all above 600mm. The maximum drop height of a 32g steel ball at nine points can reach 1100mm, the maximum drop height of a whole machine with 180-grit sandpaper can reach 1700mm, and the maximum drop height of a whole machine with 80-grit sandpaper can reach 1300mm.

[0327] Figure 5 The graph shows the compressive stress distribution of the chemically strengthened glass-ceramic prepared in Example 1. As can be seen from the graph, there is a high compressive stress (CS) of 330.716 MPa and a DOL0 of 98.963 μm near the glass surface. This high compressive stress helps to improve the glass's scratch resistance and crack propagation resistance.

[0328] The light transmittance of the chemically strengthened glass-ceramic sample prepared in Example 1 is shown in the spectral transmittance spectrum. Figure 6 As shown in the figure, the transmittance of the chemically strengthened glass-ceramic sample at a wavelength of 550 nm is 91.25%.

[0329] Safety tests were also conducted on the chemically strengthened glass-ceramic samples prepared in Example 4. Through safety experiments on the glass samples before and after the time interval when CTLD-max = 65319 MPa / mm in Example 4, it was found that their breakage conditions were within the range of safe glass. Therefore, after ion exchange, the glass CTLD_max = CTLD_saf. The safety breakage verification results are shown below. Figure 7 As shown.

[0330] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A chemically strengthened microcrystalline glass, characterized in that, The chemically strengthened glass-ceramic includes a glass-ceramic matrix and a compressive stress layer formed on the surface of the matrix through ion exchange chemical strengthening, wherein: The microcrystalline glass substrate comprises crystal group 1 and crystal group 2. The crystal family 1 includes ZnAl2O4, MgAl2O4 and (Zn,Mg)Al2O4. Crystal group 2 includes zirconium oxide; The compressive stress layer has a CTLD_saf value of 15000~70000 MPa; The microcrystalline glass matrix exhibits a total crystallinity of at least 53 wt%.

2. The chemically strengthened microcrystalline glass according to claim 1, characterized in that, Crystal family 1 also includes (Zn) crystals. 0.647 Mg 0.225 Al 0.128 (Al) 1.87 Mg 0.13 )O4.

3. The chemically strengthened microcrystalline glass according to claim 1, characterized in that, The zirconium oxide included in crystal group 2 is one or more of monoclinic zirconium oxide, tetragonal zirconium oxide, and cubic zirconium oxide.

4. The chemically strengthened microcrystalline glass according to claim 1, characterized in that, The CTLD_saf of the chemically strengthened microcrystalline glass is 30000~70000 MPa.

5. The chemically strengthened microcrystalline glass according to claim 4, characterized in that, The CTLD_saf of the chemically strengthened microcrystalline glass is 45000~65000 MPa.

6. The chemically strengthened microcrystalline glass according to claim 1, characterized in that, The chemically strengthened glass-ceramic also possesses at least one of the following mechanical properties: DOL0: 75~110μm; CT-CV: 55~140 MPa; CS: 100~470 MPa; CS50: 35~170 MPa; CT-AV: 25~110 MPa; 4PB flexural strength: 510~840 MPa.

7. The chemically strengthened microcrystalline glass according to claim 6, characterized in that, The chemically strengthened glass-ceramic also possesses at least one of the following impact resistance properties: The drop height of a 32g steel ball at nine o'clock is 600~1100 mm. Drop height of 180-grit sandpaper: 700~1700mm; Drop height of 80-grit sandpaper: 600~1300 mm.

8. The chemically strengthened microcrystalline glass according to any one of claims 1-7, characterized in that, The crystals of all phases in the microcrystalline glass matrix are combined to form composite particles with an average particle size of 15~50nm.

9. The chemically strengthened microcrystalline glass according to claim 8, characterized in that, Crystal family 1 has an average crystal size of less than 10 nm, crystal family 2 has an average crystal size of less than 8 nm, and the average crystal size of crystal family 1 is greater than the average crystal size of crystal family 2.

10. The chemically strengthened microcrystalline glass according to claim 9, characterized in that, Based on a total molar percentage of 100 mol% for all components in the glass-ceramic matrix, the glass-ceramic matrix contains the following components: SiO2: 35 mol%~55 mol%; CaO: 0~5 mol%; Al2O3: greater than 20 mol% and less than or equal to 30 mol%; B2O3: 0~3 mol%; P2O5: 0~2 mol%; ZrO2: 2 mol% ~ 7 mol%; MgO: 3 mol%~12 mol%; ZnO: 5 mol% ~ 16 mol%; BaO: 0~3 mol%; Na₂O: greater than or equal to 0 and less than 2 mol%; Li₂O: 4 mol% ~ 10 mol%; K2O: 0~5 mol%; Y2O3: 0~1 mol%; La2O3: 0~1 mol%; SrO: 0~3 mol%; Clarifying agent: 0~0.3 mol%; The clarifying agent is at least one selected from SnO2, NaCl, CeO2, and Sb2O3, and The composition of the microcrystalline glass matrix satisfies the following relationship: The [Al2O3] / [SiO2] ratio is between 0.4 and 0.

85. The value of {[ZnO]+[MgO]} / [Al2O3] is between 0.4 and 0.

9. The ratio of [R₂O] to [Al₂O₃] is between 0.2 and 0.

45. [R'O] / [Al2O3] is a value between 0.45 and 0.95, where: [Al2O3] indicates the molar percentage content of Al2O3 in the microcrystalline glass matrix; [SiO2] represents the molar percentage content of SiO2 in the glass-ceramic matrix; [ZnO] indicates the molar percentage content of ZnO in the glass-ceramic matrix; [MgO] represents the molar percentage content of MgO in the microcrystalline glass matrix; R2O can be Li2O, Na2O, or K2O, and [R2O] represents the molar percentage content of R2O in the microcrystalline glass matrix. R'O can be MgO, ZnO, CaO, BaO, or SrO, and [R'O] represents the molar percentage content of R'O in the microcrystalline glass matrix.

11. The chemically strengthened glass-ceramic according to claim 10, characterized in that, The molar percentage content of Al2O3 is 24 mol%~27 mol%. The molar percentage content of Li2O is 6.1 mol%~8 mol%. The value of [R2O] / [Al2O3] is between 0.23 and 0.

38.

12. The chemically strengthened microcrystalline glass according to claim 8, characterized in that, The chemical fortification uses a salt bath of KNO3 and / or NaNO3.

13. The chemically strengthened glass-ceramic according to claim 12, characterized in that, The chemical fortification is carried out according to the following method: The microcrystalline glass substrate is placed in the salt bath at 400~450℃ and kept for 150~300 min.

14. The chemically strengthened microcrystalline glass according to claim 13, characterized in that, The salt bath is 100 wt% NaNO3 or a composite salt bath containing 20-70 wt% KNO3 and 80-30 wt% NaNO3.

15. The chemically strengthened glass-ceramic according to claim 13, characterized in that, The microcrystalline glass substrate is polished before chemical strengthening.

16. A portable electronic device, characterized in that, The portable electronic device comprises the chemically strengthened microcrystalline glass according to any one of claims 1-15.

17. The portable electronic device according to claim 16, characterized in that, The portable electronic device is a mobile phone, tablet, or watch.

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