Brightly colored ceramic articles and methods for making same

Abstract

To provide a ceramic composition having vivid color.SOLUTION: The invention relates to a colored product made from a ceramic involving an oxide-based matrix and a doped or co-doped component of the aluminium garnet family. Also, the invention relates to a manufacturing method for the product.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to brightly colored ceramic articles, particularly watch case or movement components, made from oxide-based materials such as alumina, and to methods for making such articles. [Background technology]

[0002] Colored ceramics are typically produced industrially by mixing metal oxide matrices, such as Al2O3, ZrO2, and their composites, with color pigments. In some cases, ceramics are colored by doping with various atoms that intercalate into the crystal structure. The colors obtained in this manner are generally light. For example, yellow coloring of ceramics is often achieved by doping with praseodymium or by adding tungsten oxide and / or vanadium oxide pigments. The resulting color is usually light yellow or shifts toward orange.

[0003] An alternative solution has been proposed in the field of horology by WO 2018 / 172428, which discloses the production of vibrantly colored ceramic parts by incorporating pigments that are encapsulated in a metal oxide matrix adapted to transmit light. More precisely, this method involves the use of unconventional sintering under pressure to densify the material, a process that is complex to implement industrially. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 172428 Summary of the Invention [Problem to be solved by the invention]

[0005] It is an object of the present invention to provide novel, brightly colored ceramic compositions from which articles are made using costly methods. [Means for solving the problem]

[0006] More precisely, the invention relates to colored articles made from ceramics comprising an oxide-based matrix and doped or co-doped components of the aluminum garnet family.

[0007] More specifically, doped or co-doped elements of the aluminum garnet family, such as cerium-doped yttrium aluminum garnet (YAG:Ce), impart vibrant and vivid colors to oxide-based ceramics. These coloring elements not only replace traditional color pigments, but also allow for greater shades to be achieved and a significantly broader range of possible colors. Furthermore, the development of composites by adding oxide-based matrices eliminates the need for pure YAG, which translates into significant cost savings and improvements in toughness and machinability.

[0008] Doping aluminum garnet family components with chromium or elements from the lanthanoid group, such as cerium, neodymium, erbium, holmium, and ytterbium, results in intense, vivid colors. In particular, doping with cerium results in a yellow color. This vibrant color cannot be achieved by mixing commercially available pigments or by doping with a different element. Doping with neodymium results in a violet color, and doping with chromium results in green to red colors, depending on the oxidation state. Doping with erbium results in a pink color. Doping with ytterbium results in a green color. Co-doping with chromium and one or more additional elements selected from the lanthanoid group, such as cerium, erbium, ytterbium, holmium, and neodymium, allows for tuning of these colors and thereby expands the range of colors available. Therefore, the use of doped or co-doped aluminum garnet family components allows for re-emissive, vibrant, and clear colors to be obtained.

[0009] Thus, articles obtained using these various dopants have vibrant colors, with the L component of the Lab color space being 80 or greater, preferably 85 or greater, and more preferably 90 or greater.

[0010] The hardness is 1000 HV10 or more, preferably 1200 HV10 or more, and more preferably 1550 HV10 or more.

[0011] Toughness K iC is between 1.7 and 6 MPa√m, typically between 2 and 4.5 MPa√m.

[0012] The present invention also relates to a method for producing the article, the method comprising: - preparing, optionally in a liquid medium, a base mixture, also called a first mixture, comprising oxides and doped or co-doped components of the aluminum garnet group; forming a second mixture comprising the first mixture and an organic binder system; granulating the second mixture; forming a blank having the shape of the article; sintering the blank in air at a holding temperature of 1500 to 1800°C, preferably 1600 to 1700°C, for 20 minutes to 20 hours, preferably 1 hour to 5 hours; Includes:

[0013] The proposed method of powder mixing and conventional sintering can be easily industrialized and has a lower economic impact than current methods, such as SPS (spark plasma sintering) or production using compositions containing pure YAG.

[0014] Other features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 shows a timepiece including a middle case made of ceramic material according to the invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention relates to an article made from an oxide-based ceramic material. The article may be a decorative article such as a component of a watch, jewelry, a metal band, or more generally, the outer part of a portable element such as the outer shell of a mobile phone. In the field of watchmaking, the article may be an outer part such as a case middle, case back, bezel, crown, bridge, push button, bracelet link, dial, hands, dial index, etc. For illustrative purposes, a case middle made using the ceramic material according to the invention is shown in Figure 1. The article may also consist of a component part of a movement such as a plate or oscillator.

[0017] The ceramic material comprises an oxide-based matrix. The oxides can be ZrO2, Al2O3, TiO2, SiO2, MgAl2O4, and ZnO, or mixtures of these oxides, such as Al2O3 + ZrO2. In the presence of zirconia (ZrO2), the mixture is typically stabilized with yttrium, cerium, calcium, or magnesium. Preferably, the matrix is ​​Al2O3-based. The ceramic material further comprises a doped or co-doped phosphorescent dye component of the aluminum garnet family. The weight percentage of the doped or co-doped component of the aluminum garnet family is 5 to 85%, preferably 5 to 70%, and more preferably 10 to 60%, based on the total weight of the ceramic material. Thus, the ceramic material comprises 15 to 95 wt. %, preferably 30 to 95 wt. %, more preferably 40 to 90 wt. % oxide and 5 to 85 wt. %, preferably 5 to 70 wt. %, more preferably 10 to 60 wt. % doped or co-doped component of the aluminum garnet group.

[0018] The aluminum garnet may be yttrium aluminum garnet (YAG) or lutetium aluminum garnet (LuAG). Preferably, it is yttrium aluminum garnet. These garnets are doped or co-doped with one or more elements of the lanthanide group, cerium, neodymium, holmium, erbium, and ytterbium, respectively, or chromium. Preferably, the garnet is doped with cerium. More preferably, it is yttrium aluminum garnet doped with cerium. Even more preferably, the article comprises an alumina-based matrix (Al2O3) and yttrium aluminum garnet doped with cerium (YAG:Ce). The ceramic may also contain possible impurities, the content of which is 0.2% by weight or less, or 0.1% by weight or less.

[0019] Advantageously, the ceramic consists of an oxide-based matrix, doped or co-doped elements of the garnet family, and possible impurities. Preferably, the ceramic consists of an alumina-based matrix (Al2O3) and yttrium aluminum garnet doped with cerium (YAG:Ce), and possible impurities.

[0020] According to the present invention, the garnet group element is doped with one of the above elements, and optionally co-doped with one or more of the above elements. The total atomic percentage of the dopant and possible co-dopant or co-dopants for this element is 0.1 to 50%. If a yellow color is desired, cerium is used for doping. Preferably, for doping with cerium, the atomic percentage relative to the garnet group element is 0.5 to 10%, more preferably 1 to 5%. If a green to red color is desired, chromium is used for doping, depending on the degree of oxidation. For chromium doping, the atomic percentage relative to the garnet group element is 0.1 to 50%. If a violet color is desired, neodymium is used for doping. Preferably, the atomic percentage relative to the element is 0.9 to 11%. If a pink color is desired, erbium is used for doping, and the atomic percentage relative to the element is 0.1 to 50%. If a green coloration is desired, ytterbium is used for doping, with an atomic percentage of 0.1 to 50% of the element. The addition of a co-dopant allows for a change in color. For example, a garnet family element can be doped with cerium and co-doped with neodymium.

[0021] The article having one or more dopants has a vibrant color, with the L component of the Lab color space being 80 or greater, preferably 85 or greater, more preferably 90 or greater. The hardness is 1000 HV10 or greater, preferably 1200 HV10 or greater, more preferably 1550 HV10 or greater. For an aluminum oxide matrix with cerium-doped yttrium aluminum garnet, the hardness is 1400 HV10 or greater, preferably 1550 HV10 or greater. For a zirconium oxide matrix with cerium-doped yttrium aluminum garnet, the hardness is 1250 HV10 or greater, preferably 1400 HV10 or greater. Similarly, for an aluminum oxide and zirconia matrix with cerium-doped yttrium aluminum garnet, the hardness is 1250 HV10 or greater, preferably 1400 HV10 or greater. The article has a toughness K iCFor an aluminum oxide matrix with cerium-doped yttrium aluminum garnet, the toughness K iC For aluminum oxide and zirconia matrices with cerium-doped yttrium aluminum garnet, the toughness K iC The toughness K is also higher than 2.5 MPa√m for the zirconium oxide matrix with cerium-doped yttrium aluminum garnet. iC The density of the article is 95% or more, preferably 97% or more, and more preferably 98% or more.

[0022] The ceramic article having an alumina matrix and cerium-doped yttrium aluminum garnet has a L chromaticity of 1.0001 in the CIELAB color space (in accordance with CIE No. 15, ISO 7724 / 1, DIN 5033 Part 7, and ASTM E-1164 standards). * component is 85 or more, preferably 90 or more, a * component is -5 to 15, preferably -5 to 12, and b * The component has a yellow color of 65 to 110, preferably 70 to 97.

[0023] Additionally, ceramic articles having an alumina and zirconia matrix and cerium-doped yttrium aluminum garnet exhibit a L 0.5 saturation in the CIELAB color space (in accordance with CIE No. 15, ISO 7724 / 1, DIN 5033 Part 7, and ASTM E-1164 standards). * component is 85 or more, preferably 90 or more, a * component is -5 to 5, preferably -5 to 2, and b * The component has a yellow color of 45 to 80, preferably 50 to 70.

[0024] The article is produced by sintering using a method consisting of: A base mixture, also called a first mixture, is prepared, optionally in a liquid medium, comprising the various components described above. A second mixture is formed that includes the first mixture and an organic binder system (paraffin, polyethylene, polyvinyl acetate, etc.). The second mixture is granulated, for example in an atomizer, and dried if necessary. Preferably, the granules have a size of d50 between 10 and 100 μm, preferably between 40 and 60 μm. This second granulated mixture is forced into the desired shape to form a blank, for example by injection or pressing. Preferably, the forming is carried out by uniaxial pressing and / or cold isostatic pressing (CIP). Sintering the blank in air at a holding temperature of 1500 to 1800°C, preferably 1600 to 1700°C, for 20 minutes to 20 hours, preferably 1 to 5 hours. This process allows achieving a density of more than 97% compared to the theoretical density. This process can be preceded by a thermal debinding step in the temperature range of 200 to 1200°C. In the case of injection molding, solvent debinding is also possible. Optionally, the blank is pressed using hot isostatic pressing (HIP) at a temperature of 50 to 150°C below the sintering temperature to improve the final density of the blank.

[0025] The resulting blank is cooled and can then be machined, polished, and, if necessary, decorated to produce the desired product. Because the color is present within the blank, these finishing operations do not alter the final color of the product.

[0026] Tests were performed on ceramics containing alumina and cerium-doped yttrium aluminum garnet with a cerium-doped yttrium aluminum garnet (YAG:3Ce) content of 10 to 60% by weight. Tests were also performed on ceramics containing yttrium-stabilized alumina and zirconia matrices, as well as cerium-doped yttrium aluminum garnet with a 50% by weight content of cerium-doped yttrium aluminum garnet (YAG:3Ce). Tests were also performed on ceramics containing zirconia matrix and cerium-doped yttrium aluminum garnet with a 20% by weight content of cerium-doped yttrium aluminum garnet. In all of these tests, the doping was 3 atomic % relative to the garnet, and the zirconia was stabilized. The results are shown in Table 1 below. Hardness measurements are in HV10 hardness. Toughness was calculated using the formula:

[0027] TIFF0007741133000001.tif10170

[0028] The hardness was determined by measuring the length of the cracks at the four ends of the diagonal of the hardness indentation, where P is the applied load (N), a is half the diagonal (m), and l is the measured crack length (m).

[0029] The Lab colorimetric values ​​of the polished samples were obtained using a CM-3610A spectrophotometer under the following conditions: SCI (specular reflection included) and SCE (specular reflection excluded) measurements, tilt 8°, and a measurement area MAV of 4 mm diameter.

[0030] The samples were sintered in air at 1600 to 1700°C for 2 to 4 hours. All the samples were yellow in color. Colorimetric measurements showed very high brightness. * The L value of zirconia colored by adding praseodymium oxide is * The value was over 90 compared to a value of about 80. Also, colorimetry showed a very yellowish color, which is consistent with the b value of zirconia colored by the addition of praseodymium oxide. * Compared with the b value of about 30 for the alumina matrix *The yellow color component is greater than 75. This yellow color component is enhanced by increasing the cerium-doped yttrium aluminum garnet content. On the other hand, the toughness and hardness decrease with increasing content. Thus, the properties and color can be adjusted by adjusting the content of cerium-doped yttrium aluminum garnet according to the needs of the application.

[0031] For the matrix containing zirconia, the yellow color is slightly less intense, and b * The value is about 50, which is higher than the 30 of zirconium colored by the addition of praseodymium oxide. The hardness can exceed 1250 HV10. The toughness can exceed 2.5 MPa√m.

[0032] TIFF0007741133000002.tif114170 ** Not measured Table 1 [Explanation of symbols]

[0033] 1 Middle Case

Claims

1. A colored article made of ceramic comprising an oxide-based matrix composed of ZrO2, Al2O3, TiO2, SiO2, MgAl2O4 and ZnO, or mixtures thereof, and doped or co-doped aluminum garnet group components, the article comprising a component of a watch case or movement, or a component of a jewel.

2. 2. The article of claim 1, wherein the ceramic comprises 15 to 95 wt. % of the oxide-based matrix and 5 to 85 wt. % of the doped or co-doped element of the aluminum garnet family.

3. 2. The article of claim 1, wherein the ceramic comprises an oxide-based matrix in a content of 30 to 95% by weight and an aluminum garnet group doped or co-doped element in a content of 5 to 70% by weight.

4. 10. The article of claim 1, wherein said aluminum garnet family member is doped or co-doped with one or more elements, the total atomic percentage of all said elements being from 0.1 to 50% of said aluminum garnet family member.

5. 10. The article of claim 1, wherein the doped or co-doped aluminum garnet family includes lutetium aluminum garnet and yttrium aluminum garnet, and the doping or co-doping element is selected from chromium or an element of the lanthanide family.

6. 6. The article of claim 5, wherein said elements of the lanthanide group are selected from cerium, neodymium, erbium, holmium, and ytterbium.

7. 7. The article of claim 6, wherein the atomic percentage of neodymium doping relative to said element of the aluminum garnet family is between 0.5 and 10%.

8. 7. The article of claim 6, wherein the atomic percentage of neodymium doping relative to the aluminum garnet group element is between 0.9 and 11%.

9. 2. The article of claim 1, wherein the ceramic comprises a matrix based on aluminum oxide, zirconium oxide, or stabilized zirconium oxide, or a mixture of these oxides.

10. 7. The article of claim 6, wherein the ceramic comprises an aluminum oxide-based matrix and / or a cerium-doped yttrium aluminum garnet with co-doping elements.

11. 10. The article of claim 1, wherein said ceramic comprises said oxide-based matrix and said doped or co-doped components of the aluminum garnet family and possible impurities.

12. The ceramic is L of the CIELAB color space. ＊ 10. The article of claim 1, characterized in that the component is 80 or greater.

13. The ceramic is a color space of CIELAB color space ＊ Components are -5 to 15, b ＊ 11. The article of claim 10, wherein the composition is 65 to 110.

14. The article of claim 1 , wherein the ceramic has a hardness of 1000 HV10 or greater.

15. The ceramic has a toughness K of 1.7 to 6 MPa√m. ｉＣ 10. The article of claim 1, comprising:

16. 2. A method for manufacturing an article according to claim 1, comprising the steps of: - preparing, optionally in a liquid medium, a base mixture, also called first mixture, comprising the oxide according to any one of claims 1 to 11 and the doped or co-doped component of the aluminum garnet group; forming a second mixture comprising the first mixture and an organic binder system; granulating the second mixture; - forming a blank having the shape of the article; sintering the blank in air at a holding temperature of 1500 to 1800°C for 20 minutes to 20 hours; A method comprising:

17. 17. The method of claim 16, further comprising, after the sintering step, a hot isostatic pressing (HIP) step at a temperature of 50 to 150°C lower than the sintering temperature.

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