Photochromic transparent ceramic as well as preparation method and application thereof

Abstract

The invention relates to the technical field of transparent ceramic materials, in particular to photochromic transparent ceramic as well as a preparation method and application thereof. The preparation method of the photochromic transparent ceramic comprises the following steps: mixing a transparent ceramic base material and an additive to prepare a biscuit, and then carrying out cold isostatic pressing, sintering, hot isostatic pressing and annealing treatment, the molar ratio of the transparent ceramic base material to the additive is (99.9 to 99.99): (0.01 to 0.1); the additive is XZ2; x is selected from at least one of Ca, Sr, Ba and Mg, and Z is selected from at least one of F and Cl. According to the photochromic transparent ceramic disclosed by the invention, hydroxyl (-OH) is introduced into the ceramic as an intermediate state through the specific additive, so that the inherent contradiction of mutual competition between the color change contrast ratio and the light transmittance is solved, and the prepared ceramic has high light transmittance and high photochromic contrast ratio.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of transparent ceramic materials, in particular to a photochromic transparent ceramic and a preparation method and application thereof. BACKGROUND

[0002] The development of photochromic performance of transparent ceramics has long been limited by the inherent contradictions of the traditional oxygen vacancy defect mechanism. Taking KNN (K 0.5 Na 0.5 NbO3) based ceramics as an example, its photochromic behavior depends on the oxygen vacancies (VOs) formed during high-temperature sintering as electron traps, and the color change response is realized through electron capture and release of oxygen vacancy defect energy levels. However, this mechanism has two inherent contradictions: 1. Incompatibility between transmittance and oxygen vacancy concentration: Excessive oxygen vacancies will significantly increase light scattering centers, resulting in a sharp drop in visible light transmittance to below 50%; while low oxygen vacancy concentration can maintain high transmittance (>80%), but it loses color change ability due to insufficient defect energy levels.

[0003] 2. Process instability of element volatilization: K / Na elements in KNN ceramics are prone to volatilize during high-temperature sintering, which exacerbates the unevenness of oxygen vacancy distribution and causes lattice distortion and degradation of optical performance.

[0004] In the current application of photochromic transparent ceramics to three-dimensional optical information storage, how to coordinate the inherent contradictions between color change contrast and transmittance has become a key challenge. Therefore, the development of a kind of transparent ceramic material with high transmittance and high photochromic contrast is of great significance for promoting its application in the field of three-dimensional optical information storage.

[0005] In view of this, the present application is proposed. SUMMARY

[0006] The purpose of the present application is to provide a photochromic transparent ceramic and a preparation method and application thereof. The present application breaks through the design limitations of the oxygen vacancy defect mechanism and realizes the synergistic optimization of the transmittance and photochromic contrast of the ceramic, laying a material foundation for the development of new intelligent optical devices.

[0007] In order to achieve the above purpose of the present application, the first aspect of the present application provides a preparation method of a photochromic transparent ceramic, comprising the following steps: Mixing a transparent ceramic base material and an additive to make a green body, then performing cold isostatic pressing, sintering, hot isostatic pressing and annealing treatment to obtain the photochromic transparent ceramic; The molar ratio of the transparent ceramic base material to the additive is (99.9-99.99):(0.01-0.1); The additive is XZ2; X is at least one selected from Ca, Sr, Ba and Mg, and Z is at least one selected from F and Cl.

[0008] Further, the molar ratio of the transparent ceramic base material to the additive is (99.95-99.99):(0.01-0.05).

[0009] Further, the transparent ceramic base material comprises at least one of YAG ceramic base material, Y2O3 ceramic base material, Lu2O3 ceramic base material, Sc2O3 ceramic base material and ZrO2 ceramic base material.

[0010] Further, in the annealing process, the atmosphere is an oxygen-containing atmosphere, the annealing temperature is 1350-1450℃, and the annealing time is 5-15h.

[0011] Further, in the sintering, the sintering temperature is 1700-1750℃, and the sintering time is 5-15h.

[0012] The second aspect of the present application provides a photochromic transparent ceramic prepared by the preparation method of the photochromic transparent ceramic provided in the first aspect of the present application.

[0013] Further, the photochromic transparent ceramic has a light transmittance ≥80% in the range of 400-750nm visible light.

[0014] Further, the photochromic ceramic has a photochromic contrast ≥60% before and after irradiation of a 248nm light source, preferably ≥90%.

[0015] The third aspect of the present application provides an application of the photochromic transparent ceramic provided in the second aspect of the present application in intelligent optical devices.

[0016] The fourth aspect of the present application provides a method for improving the photochromic contrast of a transparent ceramic, comprising the following steps: Mixing a transparent ceramic base material and an additive to prepare a green body, and then performing cold isostatic pressing, sintering, hot isostatic pressing and annealing treatment; The molar ratio of the transparent ceramic base material to the additive is (99.9-99.99):(0.01-0.1). The additive is XZ2; X is at least one selected from Ca, Sr, Ba and Mg, and Z is at least one selected from F and Cl.

[0017] Compared with the prior art, the present application has the following beneficial effects: (1) In the photochromic transparent ceramic of the present application, the specific additive is used to introduce hydroxyl (-OH) as an intermediate state in the ceramic, so as to solve the inherent contradiction between photochromic contrast and light transmittance; specifically, the hydroxyl can form a stable lattice structure in the lattice before light, so that the ceramic has high light transmittance; after light, the hydroxyl absorbs holes to become free radicals, generating more oxygen vacancies, thereby improving the photochromic contrast of the ceramic, and further making the ceramic have high light transmittance and high photochromic contrast. (2) The photochromic transparent ceramic obtained by the method of the present application has a photochromic contrast of up to 92.3% on the basis of a light transmittance of more than 80%, and the comprehensive performance is much higher than that of the existing KNN photochromic transparent ceramic, and has a broad prospect in the fields of intelligent light window, anti-counterfeiting and information storage. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the specific embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0019] Figure 1 The photochromic transparent ceramic Y2O3:Ca provided for the present application embodiments 1-4 2+ The XRD pattern of pure Y2O3 provided in Comparative Example 1; Figure 2 The photochromic transparent ceramic Y2O3:Ca provided for the present application embodiments 1-4 2+ The transmittance spectrum and physical picture of pure Y2O3 provided in Comparative Example 1; Figure 3 The photochromic transparent ceramic Y2O3:Ca provided for the present application embodiments 1-4 2+ The transmittance spectrum and physical picture of pure Y2O3 provided in Comparative Example 1 before and after 248nm irradiation (irradiation time is 120s); Figure 4 The photochromic transparent ceramic Y2O3:Ca provided for the present application embodiments 1-4 2+ The FTIR spectrum of pure Y2O3 provided in Comparative Example 1; Figure 5 The photochromic transparent ceramic Y2O3:Ca provided for the present application embodiments 1-4 2+The FTIR spectra of pure Y2O3 provided by Comparative Example 1 before and after irradiation at 248 nm (irradiation time is 120 s) are compared; wherein (a)-(e) are the FTIR spectra of the transparent ceramics of Comparative Example 1 and Examples 1-4 before and after irradiation at 248 nm (irradiation time is 120 s). DETAILED DESCRIPTION

[0020] The technical solutions of the present application will be described clearly and completely below in combination with the drawings and specific embodiments, but those skilled in the art will understand that the following described embodiments are part of the embodiments of the present application, not all the embodiments, and are only used to illustrate the present application, and should not be regarded as limiting the scope of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application. The specific conditions are not specified in the examples, and are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not specified by the manufacturer, and are all conventional products that can be purchased on the market.

[0021] In view of the inherent contradiction between photochromic contrast and transmittance of the existing photochromic transparent ceramics, the present application proposes a new design method of photochromic transparent ceramics with high transmittance and high photochromic contrast, which introduces hydroxyl (-OH) as an intermediate state in the ceramics through specific additives, thereby ensuring high transmittance of the transparent ceramics while realizing high-performance photochromic properties.

[0022] Based on this, the present application provides a preparation method of photochromic transparent ceramics, comprising the following steps: mixing a transparent ceramic base material and an additive to form a green body, then performing cold isostatic pressing, sintering, hot isostatic pressing and annealing treatment to obtain the photochromic transparent ceramics. The molar ratio of the transparent ceramic base material to the additive is (99.9-99.99):(0.01-0.1). The additive is XZ2; X is selected from at least one of Ca, Sr, Ba and Mg, and Z is selected from at least one of F and Cl.

[0023] In the photochromic transparent ceramics of the present application, hydroxyl (-OH) is introduced as an intermediate state in the ceramics through specific additives, thereby solving the inherent contradiction between photochromic contrast and transmittance; specifically, the hydroxyl can form a stable lattice structure in the lattice before irradiation, so that the ceramic has high transmittance; after irradiation, the hydroxyl absorbs holes to become free radicals, generating more oxygen vacancies, thereby improving the photochromic contrast of the ceramic, and further making the ceramic have both high transmittance and high photochromic contrast.

[0024] In the specific embodiments of the present application, the additive is XZ2; X is selected from at least one of Ca, Sr, Ba and Mg, and Z is selected from at least one of F and Cl, for example, the additive can be at least one of CaCl2, CaF2, SrCl2, SrF2, BaCl2, BaF2, MgCl2 and MgF2. With the above-mentioned additive, hydroxyl groups can be introduced into the ceramic, which occupy oxygen ion lattice sites to form a stable lattice structure. Compared with oxygen vacancies, the structure is stable and is not prone to lattice collapse, which not only helps to ensure high light transmittance, but also enables higher photochromic contrast after irradiation. Specifically, the above-mentioned additive is incorporated into the ceramic matrix. Taking Y2O3 as an example, under the coordination of monovalent anions, divalent metal cations replace Y 3+ The oxygen vacancies thus generated can adsorb water molecules in the ceramic base powder and promote the hydrolysis of water molecules into H + and OH - OH - is captured by the oxygen vacancies to form hydroxyl groups, and H + and lattice O also form hydroxyl groups.

[0025] In the specific embodiments of the present application, the molar ratio of the transparent ceramic base to the additive is (99.9-99.99):(0.01-0.1), for example, it can be 99.99:0.01, 99.985:0.015, 99.98:0.02, 99.975:0.025, 99.97:0.03, 99.96:0.04, 99.95:0.05, 99.92:0.08, 99.9:0.1 or a range composed of any two of them, and is preferably (99.95-99.99):(0.01-0.05), which is more conducive to balancing the high light transmittance and high photochromic contrast of the ceramic. Among them, the number of moles of the transparent ceramic base is calculated based on the number of moles of the transparent ceramic that can be formed by the transparent ceramic base.

[0026] In the specific embodiments of the present application, the transparent ceramic base includes at least one of YAG ceramic base, Y2O3 ceramic base, Lu2O3 ceramic base, Sc2O3 ceramic base and ZrO2 ceramic base.

[0027] The transparent ceramic base refers to the raw material that can form the corresponding transparent ceramic. For example, the YAG ceramic base includes Y2O3 and Al2O3, the Y2O3 ceramic base includes Y2O3, the Lu2O3 ceramic base includes Lu2O3, the Sc2O3 ceramic base includes Sc2O3, and the ZrO2 ceramic base includes ZrO2.

[0028] In the specific embodiments of the present application, the transparent ceramic base material and the additives are mixed to form a green body, for example, the transparent ceramic base material and the additives are mixed in stoichiometric ratio, ball-milled, and then subjected to a pressing process to obtain the green body.

[0029] In the specific embodiments of the present application, the ball-milling is wet ball-milling, and the ball-milling is followed by a drying process to obtain a powder. The powder is subjected to a pressing process to obtain the green body.

[0030] In the specific embodiments of the present application, the wet ball-milling is a general technique for mixing and refining powder, i.e., the powder of different proportions, the ball-milling medium, and an appropriate amount of dispersant are placed in a ball mill to achieve uniform mixing of the powder. In the subsequent examples, a planetary ball mill is only used as an example for wet ball-milling, and a person skilled in the art can choose different ball mills according to actual needs; in the subsequent examples, zirconium dioxide is only selected as the ball-milling medium and the ball-to-powder ratio is 1:3, and a person skilled in the art can make routine adjustments according to the actual mixing state; in the subsequent examples, ethanol is only selected as the dispersant and the mass ratio of the dispersant to the total amount of the mixed material (transparent ceramic base material and additives) is 1:1, and a person skilled in the art can make routine adjustments according to the actual mixing state; in the subsequent examples, the ball-milling time is only selected as 15 h, and a person skilled in the art can make routine adjustments according to the actual mixing state.

[0031] In the specific embodiments of the present application, the green body is subjected to cold isostatic pressing. Further, in the cold isostatic pressing, the pressure is 150-250 MPa, for example, it can be 150 MPa, 180 MPa, 200 MPa, 220 MPa, 250 MPa, or a range formed by any two of them. Further, after cold isostatic pressing, a preform with a relative density of 54%-56% is obtained.

[0032] In the specific embodiments of the present application, the preform after cold isostatic pressing is subjected to sintering. Further, in the sintering, the sintering temperature is 1700-1750℃, for example, it can be 1700℃, 1710℃, 1720℃, 1730℃, 1740℃, 1750℃, or a range formed by any two of them, and the sintering time is 5-15 h, for example, it can be 5 h, 8 h, 10 h, 12 h, 15 h, or a range formed by any two of them. Further, the sintering is vacuum sintering.

[0033] In the specific embodiment of the present application, after sintering, hot isostatic pressing is performed. Further, in the hot isostatic pressing, the temperature is 1600-1700℃, for example, it can be 1600℃, 1620℃, 1650℃, 1680℃, 1700℃ or a range consisting of any two of them, the pressure is 180-200MPa, for example, it can be 180MPa, 185MPa, 190MPa, 196MPa, 200MPa or a range consisting of any two of them; the time is 2-6h, for example, it can be 2h, 3h, 4h, 5h, 6h or a range consisting of any two of them. Further, the atmosphere of the hot isostatic pressing is a protective atmosphere, including but not limited to argon.

[0034] In the specific embodiment of the present application, after hot isostatic pressing, annealing treatment is performed. Further, in the annealing treatment, the atmosphere is an oxygen-containing atmosphere, the annealing temperature is 1350-1450℃, for example, it can be 1350℃, 1380℃, 1400℃, 1420℃, 1450℃ or a range consisting of any two of them; the annealing time is 5-15h, for example, it can be 5h, 8h, 10h, 12h, 15h or a range consisting of any two of them.

[0035] In the specific embodiment of the present application, in the annealing treatment, the oxygen-containing atmosphere is air.

[0036] The second aspect of the present application provides a photochromic transparent ceramic prepared by the preparation method of the photochromic transparent ceramic provided in the first aspect of the present application.

[0037] In the specific embodiment of the present application, the photochromic transparent ceramic has a transmittance ≥80% in the range of 400-750nm visible light.

[0038] In the specific embodiment of the present application, the photochromic ceramic has a photochromic contrast ≥60% before and after irradiation of a 248nm light source, preferably ≥90%, for example, it can be 90%, 90.5%, 91%, 91.5%, 92%, 92.3%, 93% or a range consisting of any two of them.

[0039] Wherein, the photochromic contrast ΔAbs refers to: ΔAbs=(R0-R1) / R0; wherein, R0 is the transmittance of the photochromic ceramic before irradiation of the light source, and R1 is the transmittance of the photochromic ceramic after irradiation of the 248nm light source for 120s.

[0040] The third aspect of the present application provides the application of the photochromic transparent ceramic provided in the second aspect of the present application in intelligent optical devices.

[0041] The fourth aspect of the present application provides a method for improving the photochromic contrast of a transparent ceramic, comprising the following steps: The transparent ceramic base material and the additive are mixed to form a green body, and then cold isostatic pressing, sintering, hot isostatic pressing and annealing treatment are carried out; The molar ratio of the transparent ceramic base material to the additive is (99.9-99.99):(0.01-0.1). The additive is XZ2; X is at least one selected from Ca, Sr, Ba and Mg, and Z is at least one selected from F and Cl.

[0042] In the preparation of the transparent ceramic, the specific additive is introduced, and a proper amount of hydroxyl group is introduced into the prepared transparent ceramic. The hydroxyl group can form a stable crystal lattice structure in the crystal lattice before light irradiation, so that the ceramic has a higher light transmittance. After light irradiation, the hydroxyl group absorbs holes to become free radicals, and more oxygen vacancies are generated, thereby improving the photochromic contrast of the ceramic. Thus, while ensuring high light transmittance, the photochromic contrast of the ceramic is improved.

[0043] In the present application, by adjusting the type and amount of the additive, a certain amount of hydroxyl group is introduced into the transparent ceramic, and a good balance between the light transmittance and the photochromic contrast of the ceramic is achieved.

[0044] The way of introducing the additive into the transparent ceramic base material, and the treatment after introducing the additive (including cold isostatic pressing, sintering, hot isostatic pressing and annealing treatment, etc.) are referred to the foregoing, and will not be repeated here.

[0045] Example 1 The present embodiment provides a preparation method of photochromic transparent ceramic, comprising the following steps: (1) Y2O3 and CaCl2 are weighed according to a molar ratio of 99.99:0.01, then ethanol (the mass of ethanol is 1 times the mass sum of Y2O3 and CaCl2) is added, zirconia small balls are added according to a ball-to-material ratio of 1:3, and the mixture is placed in a ball mill jar for ball milling for 15 h to obtain a mixed slurry; the mixed slurry is placed in a 50℃ oven for drying, and then ground to obtain a mixed powder. The mixed powder is pressed into a green body sheet through a hardened stainless steel mold.

[0046] (2) The green body sheet obtained in step (1) is subjected to cold isostatic pressing treatment under the condition of 200 MPa to obtain a preform with a relative density of 55%. Then the preform is vacuum sintered at 1730℃ for 7h.

[0047] (3) The green body after vacuum sintering in step (2) is subjected to hot isostatic pressing treatment under the condition of 1650℃ and 196 MPa for 4h in an argon atmosphere. The green body after hot isostatic pressing treatment is subjected to annealing treatment in an air atmosphere at 1400℃ for 10h, and then taken out after cooling to room temperature. Double-sided polishing treatment is performed to meet the requirements of optical testing.

[0048] Example 2 Example 2 refers to the preparation method of the photochromic transparent ceramic of Example 1, the difference is only that in step (1), the molar ratio of Y2O3 and CaCl2 is different.

[0049] In this embodiment, the molar ratio of Y2O3 and CaCl2 is 99.98:0.02.

[0050] Example 3 Example 3 refers to the preparation method of the photochromic transparent ceramic of Example 1, the difference is only that in step (1), the molar ratio of Y2O3 and CaCl2 is different.

[0051] In this embodiment, the molar ratio of Y2O3 and CaCl2 is 99.95:0.05.

[0052] Example 4 Example 4 refers to the preparation method of the photochromic transparent ceramic of Example 1, the difference is only that in step (1), the molar ratio of Y2O3 and CaCl2 is different.

[0053] In this embodiment, the molar ratio of Y2O3 and CaCl2 is 99.9:0.1.

[0054] Comparative Example 1 Comparative Example 1 refers to the preparation method of Example 1, the difference is only that in step (1), CaCl2 is not added.

[0055] Experimental Example Figure 1 The photochromic transparent ceramic Y2O3:Ca provided by Examples 1-4 of the present application 2+ The XRD pattern of pure Y2O3 provided by Comparative Example 1.

[0056] Figure 2 The photochromic transparent ceramic Y2O3:Ca provided by Examples 1-4 of the present application 2+ The transmittance spectrum and the physical picture of pure Y2O3 provided by Comparative Example 1; from the figure, it can be seen that the present application can ensure or even improve the light transmittance of the transparent ceramic by introducing an appropriate amount of additive into the transparent ceramic Y2O3. The visible light transmittance of the transparent ceramic prepared by the present application is as high as 80%, which has reached the theoretical transmittance, and it is a very good transparent medium. The ceramic physical picture also shows very high macroscopic transparency, which is highly consistent with the test data.

[0057] Figure 3 The photochromic transparent ceramic Y2O3:Ca provided by Examples 1-4 of the present application 2+The transmittance spectrum of pure Y2O3 provided by Comparative Example 1 before and after irradiation at 248 nm (irradiation time is 120 s). From the figure, it can be seen that the photochromic contrast △Abs of pure Y2O3 provided by Comparative Example 1 before and after irradiation at 248 nm is 6.6%; the photochromic transparent ceramic Y2O3:Ca 2+ The photochromic contrast △Abs is as low as 63.1% before and after irradiation at 248 nm. On the basis of the transmittance of more than 80%, the photochromic contrast △Abs can be as high as 92.3%. After the photochromic transparent ceramic is irradiated at 248 nm, it can be restored to the original color by heating treatment (450℃ / 5min).

[0058] Figure 4 The photochromic transparent ceramic Y2O3:Ca 2+ The FTIR spectrum of pure Y2O3 provided by Comparative Example 1; Figure 5 The photochromic transparent ceramic Y2O3:Ca 2+ The FTIR spectrum comparison chart of pure Y2O3 provided by Comparative Example 1 before and after irradiation at 248 nm (irradiation time is 120 s). From the figure, it can be seen that the present application introduces an appropriate amount of additive in the preparation of transparent ceramic Y2O3, and a large number of hydroxyl groups are introduced in the obtained ceramic material. Before light, the hydroxyl group can form a stable lattice structure in the lattice, so that the ceramic has a high transmittance; after light, the hydroxyl group absorbs holes to become free radicals, generating more oxygen vacancies, improving the photochromic contrast of the ceramic, and thus the ceramic has high transmittance and high photochromic contrast.

[0059] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing photochromic transparent ceramics, characterized in that, Includes the following steps: A green body is prepared by mixing transparent ceramic matrix and additives, and then subjected to cold isostatic pressing, sintering, hot isostatic pressing and annealing to obtain the photochromic transparent ceramic. The molar ratio of the transparent ceramic matrix to the additive is (99.9~99.99):(0.01~0.1). The additive is XZ2; X is selected from at least one of Ca, Sr, Ba and Mg, and Z is selected from at least one of F and Cl.

2. The preparation method according to claim 1, characterized in that, The molar ratio of the transparent ceramic matrix to the additive is (99.95~99.99): (0.01~0.05).

3. The preparation method according to claim 1, characterized in that, The transparent ceramic matrix includes at least one of YAG ceramic matrix, Y2O3 ceramic matrix, Lu2O3 ceramic matrix, Sc2O3 ceramic matrix and ZrO2 ceramic matrix.

4. The preparation method according to claim 1, characterized in that, In the annealing process, the atmosphere is an oxygen-containing atmosphere, the annealing temperature is 1350–1450℃, and the annealing time is 5–15 hours.

5. The preparation method according to claim 1, characterized in that, In the sintering process, the sintering temperature is 1700–1750℃ and the sintering time is 5–15 hours.

6. A photochromic transparent ceramic, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 5.

7. The photochromic transparent ceramic according to claim 6, characterized in that, The photochromic transparent ceramic has a transmittance of ≥80% in the visible light range of 400–750 nm.

8. The photochromic transparent ceramic according to claim 6, characterized in that, The photochromic ceramic exhibits a photochromic contrast ratio of ≥60% before and after irradiation with a 248nm light source, preferably ≥90%.

9. The application of the photochromic transparent ceramic according to any one of claims 6 to 8 in intelligent optical devices.

10. A method for improving the photochromic contrast of transparent ceramics, characterized in that, Includes the following steps: Transparent ceramic matrix and additives are mixed to form a green body, which is then subjected to cold isostatic pressing, sintering, hot isostatic pressing and annealing. The molar ratio of the transparent ceramic matrix to the additive is (99.9~99.99):(0.01~0.1). The additive is XZ2; X is selected from at least one of Ca, Sr, Ba and Mg, and Z is selected from at least one of F and Cl.

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