High-transmittance photochromic transparent ceramic as well as preparation method and application thereof

Abstract

The invention relates to the technical field of ceramic materials, in particular to high-transmittance photochromic transparent ceramic as well as a preparation method and application thereof. The preparation method of the high-transmittance photochromic transparent ceramic comprises the following steps: (a) tabletting a mixture of an oxide and an isovalent ionic compound to obtain a preform; (b) carrying out sintering treatment on the prefabricated body, and then carrying out hot isostatic pressing treatment and annealing treatment; wherein the oxide comprises at least one of Y2O3, Lu2O3 and Sc2O3, and the isovalent ionic compound comprises at least one of ZrO2, MgO and CaO; the annealing treatment is carried out in an oxygen-containing atmosphere. The invention provides a new photochromic mechanism, isovalent ions are introduced into the transparent ceramic, and positive electricity / negative electricity is utilized to capture electrons to form an electronic color center, so that photochromic of the transparent ceramic is caused; and meanwhile, the introduction of the isovalent ions can play a role in fluxing, so that the transmittance of the transparent ceramic is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic materials, and in particular to a high transmittance photochromic transparent ceramic and its preparation method and application. Background Art

[0002] With the rapid development of digital information technology in human society, the security of information during storage and transmission has become crucial for safeguarding personal interests. Compared with traditional storage media, optical storage media exhibit significant advantages in terms of storage density, service life, sustainability, and non-contact reading and writing modes. As an important branch of light-responsive materials, photochromic materials have attracted much attention due to their application potential in areas such as rewritable optical memories, information encryption, anti-counterfeiting, optical switches, visual recognition codes, and passive optical dosimeters. The photochromic phenomenon refers to the reversible transformation of the optical properties (reflectivity, absorptivity, transmittance, etc.) of a material between two different states under the alternating stimulation of light / heat.

[0003] Current research mainly focuses on two-dimensional (2D) photochromic storage based on opaque ceramics or thin films. To meet the requirements of high-capacity and high-quality optical storage and imaging, three-dimensional (3D) photochromic media, including thin films, glasses, and transparent ceramics, have received increasing attention. Compared with photochromic thin films and glasses, transparent ceramics have more excellent chemical stability and thermomechanical properties (thermal shock resistance, toughness, strength, thermal conductivity), and are more suitable for long-term information storage. However, there are few developed transparent ceramic systems at present, and the main bottleneck lies in the difficulty of simultaneously achieving high transmittance and high color change contrast. Current research focuses on the KNN (K 0.5 Na 0.5 NbO3)-based transparent ceramic system: During the high-temperature sintering process, K / Na elements volatilize to generate oxygen vacancies to maintain charge balance, forming defect energy levels within the bandgap. Its photochromism originates from the capture and release of electrons at the oxygen vacancy defect energy levels. However, excessive oxygen vacancies result in insufficient transmittance of KNN ceramics (<50% at a wavelength of 600 nm), while high-quality and high-transmittance KNN lacks sufficient oxygen vacancies, resulting in no obvious photochromic phenomenon. This contradictory characteristic of high transmittance and oxygen vacancies in KNN restricts its practical application. There is an urgent need to develop a transparent ceramic with both high transmittance and strong color change contrast.

[0004] In view of this, the present invention is specifically proposed. Summary of the Invention

[0005] The object of the present invention is to provide a high transmittance photochromic transparent ceramic and its preparation method and application. The photochromic transparent ceramic of the present invention, different from the photochromism caused by traditional oxygen vacancy defects, utilizes the electron color centers formed by the capture of positive / negative charged electrons to cause photochromism of the transparent ceramic, while significantly improving the transmittance of the transparent ceramic.

[0006] To achieve the above object of the present invention, a method for preparing a high transmittance photochromic transparent ceramic according to a first aspect of the present invention includes the following steps:

[0007] (a) Pressing a mixture of an oxide and a heterovalent ion compound to obtain a preform;

[0008] (b) Sintering the preform, and then performing hot isostatic pressing treatment and annealing treatment;

[0009] Wherein, the oxide includes at least one of Y2O3, Lu2O3 and Sc2O3, and the heterovalent ion compound includes at least one of ZrO2, MgO and CaO;

[0010] The annealing treatment is carried out in an oxygen-containing atmosphere.

[0011] In a specific embodiment of the present invention, in the annealing treatment, the temperature is 1350 - 1450 °C and the time is 5 - 15 h. Further, the annealing treatment is carried out in an air atmosphere.

[0012] In a specific embodiment of the present invention, the molar ratio of the oxide to the heterovalent ion compound is 1:(0.0001 - 0.08).

[0013] In a specific embodiment of the present invention, the pressing includes: pressing the mixture to form a green body, and then performing cold isostatic pressing treatment to obtain the preform.

[0014] In a specific embodiment of the present invention, in the cold isostatic pressing treatment, the pressure is 150 - 250 MPa. Further, the relative density of the preform is 54% - 56%.

[0015] In a specific embodiment of the present invention, the sintering treatment is vacuum sintering, the sintering temperature is 1700 - 1750 °C, and the sintering time is 5 - 10 h.

[0016] In a specific embodiment of the present invention, in the hot isostatic pressing treatment, the temperature is 1600 - 1700 °C, the pressure is 180 - 220 MPa, and the time is 2 - 6 h. Further, the atmosphere of the hot isostatic pressing treatment is an argon atmosphere.

[0017] A second aspect of the present invention provides a high transmittance photochromic transparent ceramic prepared by using the method for preparing a high transmittance photochromic transparent ceramic according to the first aspect of the present invention.

[0018] In a specific embodiment of the present invention, the transmittance of the high transmittance photochromic transparent ceramic in the visible light range of 400 - 750 nm is ≥80%.

[0019] In a specific embodiment of the present invention, after the high transmittance photochromic transparent ceramic is irradiated by a 248 nm light source for 1 s, the transmittance in the visible light range of 400-750 nm is ≥20%.

[0020] In a specific embodiment of the present invention, the maximum value of the photochromic contrast of the high transmittance photochromic transparent ceramic before and after irradiation by a 248 nm light source is 10%-15%; wherein, the calculation method of the photochromic contrast ΔR is: ΔR = (T0 - T1) / T0, where T0 is the transmittance of the high transmittance photochromic transparent ceramic before irradiation, and T1 is the transmittance of the high transmittance photochromic transparent ceramic after irradiation by a 248 nm light source for 1 s.

[0021] The third aspect of the present invention provides an application of the high transmittance photochromic transparent ceramic provided by the second aspect of the present invention in intelligent light windows, anti-counterfeiting or information storage.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) The present invention provides a new photochromic mechanism. By introducing hetero-valent ions into the transparent ceramic, electron color centers are formed by positive / negative charge trapping electrons, causing the photochromism of the transparent ceramic; at the same time, the introduction of hetero-valent ions can play a fluxing role, effectively improving the transmittance of the transparent ceramic.

[0024] (2) The high transmittance photochromic transparent ceramic prepared by the preparation method of the present invention takes into account both high transmittance and photochromic contrast, and can be well applied to the field of three-dimensional optical information storage. Description of the Drawings

[0025] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0026] Figure 1 It is an X-ray diffraction pattern of the photochromic transparent ceramic Y2O3﹕Zr provided in Example 1 of the present invention and Y2O3 of Comparative Example 1.

[0027] Figure 2 It is a transmittance spectrum of the photochromic transparent ceramic Y2O3﹕Zr provided in Example 1 of the present invention before and after irradiation at 248 nm (irradiation duration is 1 s).

[0028] Figure 3Transmittance spectra of Y2O3 in Comparative Example 1 of the present invention before and after irradiation at 248 nm (irradiation duration: 1 s);

[0029] Figure 4 The physical diagram of the photochromic transparent ceramic Y2O3﹕Zr provided in Example 1 of the present invention and Y2O3 in Comparative Example 1 after irradiation at 248 nm for 1 s. The Y2O3 in Comparative Example 1 is on the left, and the Y2O3﹕Zr in Example 1 is on the right. Specific Embodiments

[0030] The technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present invention. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0031] Aiming at the problem of low transmittance faced by existing photochromic ceramics in the application of three-dimensional optical information storage, the present invention introduces a method of introducing hetero-valent cations to endow the ceramics with photochromic properties while ensuring high transmittance.

[0032] Based on this, the first aspect of the present invention provides a method for preparing a high-transmittance photochromic transparent ceramic, including the following steps:

[0033] (a) Press a mixture of an oxide and a hetero-valent ion compound to obtain a preform;

[0034] (b) Sinter the preform, and then perform hot isostatic pressing treatment and annealing treatment;

[0035] Among them, the oxide includes at least one of Y2O3, Lu2O3, and Sc2O3, and the hetero-valent ion compound includes at least one of ZrO2, MgO, and CaO;

[0036] The annealing treatment is carried out in an oxygen-containing atmosphere.

[0037] The present invention provides a new photochromic mechanism. By introducing hetero-valent ions into transparent ceramics, positive charge centers are introduced into sesquioxide (Y2O3, Lu2O3, and Sc2O3) transparent ceramics. Electron color centers are formed by positive / negative charge capturing electrons, causing the photochromism of the transparent ceramics. At the same time, the introduction of hetero-valent ions can play a role in fluxing, effectively improving the transmittance of the transparent ceramics. Among them, oxides and hetero-valent ion compounds are mixed, pressed into tablets, sintered, etc., to introduce hetero-valent ions into the transparent ceramics, and then annealing treatment is carried out to eliminate oxygen vacancy defects in the transparent ceramics.

[0038] Compared with the existing photochromic ceramic system based on the capture of electrons by oxygen vacancy defects to cause color change, the photochromic system of the present invention has the following advantages:

[0039] (1) By hetero-valent ions occupying the original cation lattice positions, it is not easy to cause lattice collapse like oxygen vacancies; and hetero-valent ions have a higher doping concentration, bringing a greater photochromic contrast.

[0040] (2) The hetero-valent ions adopted in the present invention simultaneously have a fluxing effect, and can improve the transmittance of the ceramics while increasing the photochromic contrast.

[0041] In a specific embodiment of the present invention, during the annealing treatment, the temperature is 1350 - 1450 °C, and the time is 5 - 15 h. Further, the annealing treatment is carried out in an air atmosphere.

[0042] For example, in different embodiments, during the annealing treatment, the temperature can be 1350 °C, 1380 °C, 1400 °C, 1420 °C, 1450 °C or the range composed of any two of them, and the time can be 5 h, 6 h, 8 h, 10 h, 12 h, 15 h or the range composed of any two of them. Under the above annealing treatment conditions, oxygen vacancy defects can be effectively eliminated.

[0043] In a specific embodiment of the present invention, the molar ratio of the oxide to the hetero-valent ion compound is 1:(0.0001 - 0.08), for example, it can be 1:0.0001, 1:0.0005, 1:0.001, 1:0.005, 1:0.01, 1:0.02, 1:0.03, 1:0.04, 1:0.05, 1:0.06, 1:0.07, 1:0.08 or the range composed of any two of them. The amount of the hetero-valent ion compound is regulated within the above range to obtain a ceramic material with an optimal balance of transmittance and photochromic contrast.

[0044] In a specific embodiment of the present invention, the preparation of the mixture includes: mixing and ball-milling the oxide and the hetero-valent ion compound.

[0045] In actual operation, the conditions of the hybrid ball milling can be adjusted routinely according to the actual situation to ensure that the oxide and the heterovalent ion compound are evenly mixed. For example, the ball milling medium used for ball milling can be zirconia. During the ball milling process, the ball-to-material ratio can be controlled at 1:3, but it is not limited thereto; the dispersing solvent used for ball milling can be ethanol. During the ball milling process, the mass ratio of the dispersing solvent to the mixed material can be (1-1.2):1, but it is not limited thereto; the ball milling time can be 12-24 h.

[0046] In a specific embodiment of the present invention, the ball milling is wet ball milling. After the hybrid ball milling, a drying treatment is further included to obtain a mixture powder. Specifically, the slurry after ball milling is dried, and the powder is obtained by crushing through methods such as grinding. The drying process can be carried out in conventional equipment such as an oven.

[0047] In a specific embodiment of the present invention, the tabletting includes: pressing the mixture to form a green body, and then performing cold isostatic pressing treatment to obtain a preform.

[0048] In a specific embodiment of the present invention, the green body is formed by pressing through a mold. Further, a hardened stainless steel mold can be used for pressing to obtain the green body, but it is not limited thereto. During the process of forming the green body by pressing, the pressing pressure can be 3-20 MPa, but it is not limited thereto.

[0049] In a specific embodiment of the present invention, during the cold isostatic pressing treatment, the pressure is 150-250 MPa. For example, it can be 150 MPa, 180 MPa, 200 MPa, 220 MPa, 250 MPa, or the range composed of any two of them. Further, the relative density of the preform is 54%-56%.

[0050] Among them, the duration of the cold isostatic pressing treatment is 60-240 s, but it is not limited thereto, subject to obtaining a preform with a relative density of 54%-56%.

[0051] In a specific embodiment of the present invention, the sintering treatment is vacuum sintering. The sintering temperature is 1700-1750 °C. For example, it can be 1700 °C, 1710 °C, 1720 °C, 1730 °C, 1740 °C, 1750 °C, or the range composed of any two of them; the sintering time is 5-10 h. For example, it can be 5 h, 6 h, 8 h, 10 h, or the range composed of any two of them. Adjusting the sintering conditions within the above range is more conducive to the heterovalent ions occupying the original cation lattice sites and improving the photochromic contrast.

[0052] In actual operation, the sintering treatment can be carried out in a tube furnace.

[0053] In a specific embodiment of the present invention, during hot isostatic pressing treatment, the temperature is 1600 - 1700 °C, for example, it can be 1600 °C, 1620 °C, 1650 °C, 1680 °C, 1700 °C or the range composed of any two of them; the pressure is 180 - 220 MPa, for example, it can be 180 MPa, 190 MPa, 200 MPa, 210 MPa, 220 MPa or the range composed of any two of them; the time is 2 - 6 h, for example, it can be 2 h, 4 h, 6 h, etc. Further, the atmosphere of the hot isostatic pressing treatment is an argon atmosphere.

[0054] In a specific embodiment of the present invention, it further includes: double - side polishing the ceramic after annealing treatment to meet the requirements of optical testing.

[0055] The second aspect of the present invention provides a high - transmittance photochromic transparent ceramic prepared by using the preparation method of the high - transmittance photochromic transparent ceramic provided in the first aspect of the present invention.

[0056] In a specific embodiment of the present invention, the transmittance of the high - transmittance photochromic transparent ceramic in the visible light range of 400 - 750 nm is ≥ 80%.

[0057] In a specific embodiment of the present invention, after the high - transmittance photochromic transparent ceramic is irradiated by a 248 nm light source for 1 s, the transmittance in the visible light range of 400 - 750 nm is ≥ 20%.

[0058] In a specific embodiment of the present invention, the maximum value of the photochromic contrast of the high - transmittance photochromic transparent ceramic before and after irradiation by a 248 nm light source is 10% - 15%; wherein, the calculation method of the photochromic contrast ΔR is: ΔR=(T0 - T1) / T0, where T0 is the transmittance of the high - transmittance photochromic transparent ceramic before irradiation, and T1 is the transmittance of the high - transmittance photochromic transparent ceramic after being irradiated by a 248 nm light source for 1 s.

[0059] The photochromic transparent ceramic prepared by using the method of the present invention, on the basis that the transmittance exceeds 80%, has a photochromic contrast as high as 15%, and its comprehensive performance is far higher than that of the existing KNN photochromic transparent ceramic, and has broad prospects in the fields of intelligent light windows, anti - counterfeiting and information storage.

[0060] The third aspect of the present invention provides the application of the high - transmittance photochromic transparent ceramic provided in the second aspect of the present invention in intelligent light windows, anti - counterfeiting or information storage.

[0061] The present invention also provides a method for improving the photochromic contrast and transmittance of a transparent ceramic, including the following steps:

[0062] Press the mixture of the oxide and the heterovalent ionic compound into a tablet to obtain a preform; sinter the preform, and then perform hot isostatic pressing treatment and annealing treatment;

[0063] Adjust the dosage ratio of the oxide and the heterovalent ionic compound to obtain transparent ceramics with different photochromic contrasts and transmittances;

[0064] Among them, the oxide includes at least one of Y2O3, Lu2O3, and Sc2O3, and the heterovalent ionic compound includes at least one of ZrO2, MgO, and CaO.

[0065] Among them, the specific operations such as the preparation of the mixture, pressing, sintering treatment, hot isostatic pressing treatment, and annealing treatment are the same as those of the above-mentioned preparation method of the high-transmittance photochromic transparent ceramic, and will not be elaborated here.

[0066] The dosage ratio of the oxide and the heterovalent ionic compound can be adjusted to obtain transparent ceramics with optimal transmittance and photochromic contrast.

[0067] Example 1

[0068] This example provides a preparation method of a high-transmittance photochromic transparent ceramic, including the following steps:

[0069] (1) Weigh Y2O3 and ZrO2 according to the chemical composition (Zr 0.03 Y 0.97 )2O3 (the molar ratio of Y2O3 and ZrO2 is 0.97﹕0.06), then add ethanol, add zirconia balls according to the ball-to-material ratio of 1﹕3, place them in a ball mill jar, and perform two-way ball milling for 15 h to obtain a mixed slurry. Then dry the mixed slurry in an oven at 50 °C, and grind the dried material to obtain a powder.

[0070] (2) Press the powder obtained in step (1) into a green body sheet through a hardened stainless steel mold, and then perform cold isostatic pressing treatment under the condition of 200 MPa to obtain a preform with a relative density of 55%.

[0071] (3) Place the preform in a tube furnace, sinter it in vacuum at 1730 °C for 7 h, take it out, and then perform hot isostatic pressing treatment in an argon atmosphere at 1650 °C and 196 MPa for 4 h.

[0072] (4) Place the sample after hot isostatic pressing treatment in a tube furnace, anneal it in an air atmosphere at 1400 °C for 10 h, take it out after cooling to room temperature, and perform double-sided polishing treatment to meet the requirements of optical testing.

[0073] Example 2

[0074] This example refers to the preparation method of the high transmittance photochromic transparent ceramic of Example 1, with the only difference being that in step (1), the molar ratio of Y2O3 to ZrO2 is different.

[0075] In this example, the molar ratio of Y2O3 to ZrO2 is 1:0.01.

[0076] Example 3

[0077] This example refers to the preparation method of the high transmittance photochromic transparent ceramic of Example 1, with the only difference being that in step (1), the molar ratio of Y2O3 to ZrO2 is different.

[0078] In this example, the molar ratio of Y2O3 to ZrO2 is 1:0.08.

[0079] Example 4

[0080] This example refers to the preparation method of the high transmittance photochromic transparent ceramic of Example 1, with the only difference being that in step (4), the annealing temperature is different.

[0081] In this example, the annealing temperature is 1350 °C.

[0082] Example 5

[0083] This example refers to the preparation method of the high transmittance photochromic transparent ceramic of Example 1, with the only difference being that in step (4), the annealing temperature is different.

[0084] In this example, the annealing temperature is 1450 °C.

[0085] Comparative Example 1

[0086] Comparative Example 1 refers to the preparation method of Example 1, with the only difference being that ZrO2 is not added.

[0087] Experimental Example

[0088] Figure 1 It is the X-ray diffraction pattern of the photochromic transparent ceramic Y2O3:Zr provided in Example 1 of the present invention and Y2O3 of Comparative Example 1;

[0089] Figure 2 It is the transmittance spectrum of the photochromic transparent ceramic Y2O3:Zr provided in Example 1 of the present invention before and after irradiation at 248 nm (irradiation duration is 1 s); Figure 3Transmittance spectra of Y2O3 in Comparative Example 1 of the present invention before and after irradiation at 248 nm (irradiation duration: 1 s). As can be seen from the figure, the photochromic transparent ceramic Y2O3﹕Zr provided in Example 1 of the present invention has a transmittance as high as 84% in the visible light region of 400 - 750 nm, reaching the theoretical transmittance, and is an excellent transparent medium. The photochromic contrast of the photochromic transparent ceramic Y2O3﹕Zr provided in Example 1 of the present invention before and after irradiation with a 248 nm light source is as high as 15%. Figure 4 Photographs of the photochromic transparent ceramic Y2O3﹕Zr provided in Example 1 of the present invention and Y2O3 in Comparative Example 1 after irradiation at 248 nm for 1 s. As can be seen from the figure, the photochromic transparent ceramic Y2O3﹕Zr provided in Example 1 of the present invention has good transmittance and photochromic contrast.

[0090] From the above results, it can be seen that the present invention provides a method for developing a photochromic transparent ceramic with high transmittance. By the method of the present invention, a ceramic with high transmittance and high photochromic contrast can be obtained. Moreover, the method of the present invention has simple process, short cycle, simple and inexpensive raw materials, which is conducive to large-scale industrial production.

[0091] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some 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 invention.

Claims

1. Preparation method of high transmittance photochromic transparent ceramics, characterized in that, It includes the following steps: (a) Press a mixture of an oxide and a heterovalent ion compound to obtain a preform; (b) Sinter the preform, and then perform hot isostatic pressing treatment and annealing treatment; Among them, the oxide includes at least one of Y2O3, Lu2O3, and Sc2O3, and the heterovalent ion compound includes at least one of ZrO2, MgO, and CaO; The annealing treatment is carried out in an oxygen-containing atmosphere.

2. The preparation method according to claim 1, characterized in that, During the annealing treatment, the temperature is 1350-1450 °C and the time is 5-15 h; Preferably, the annealing treatment is carried out in an air atmosphere.

3. The preparation method according to claim 1, characterized in that, The molar ratio of the oxide to the heterovalent ion compound is 1:(0.0001-0.08).

4. The preparation method according to claim 1, wherein The pressing includes: pressing the mixture to form a green body, and then performing cold isostatic pressing treatment to obtain the preform.

5. The preparation method according to claim 4, wherein During the cold isostatic pressing treatment, the pressure is 150-250 MPa; Preferably, the relative density of the preform is 54%-56%.

6. The preparation method according to claim 1, characterized in that, The sintering treatment is vacuum sintering, the sintering temperature is 1700-1750 °C, and the sintering time is 5-10 h.

7. The preparation method according to claim 1, characterized in that, During the hot isostatic pressing treatment, the temperature is 1600-1700 °C, the pressure is 180-220 MPa, and the time is 2-6 h; Preferably, the atmosphere of the hot isostatic pressing treatment is an argon atmosphere.

8. High transmittance photochromic transparent ceramics, characterized in that, Prepared by the preparation method according to any one of claims 1-7.

9. The high transmittance photochromic transparent ceramic according to claim 8, wherein It has at least one of the following characteristics: (1) The transmittance of the high transmittance photochromic transparent ceramic in the visible light range of 400-750 nm is ≥80%; (2) After the high transmittance photochromic transparent ceramic is irradiated by a 248 nm light source for 1 s, the transmittance in the visible light range of 400-750 nm is ≥20%; (3) The maximum value of the photochromic contrast of the high transmittance photochromic transparent ceramic before and after irradiation by a 248 nm light source is 10%-15%.

10. Application of the high transmittance photochromic transparent ceramic according to claim 8 or 9 in an intelligent light window, anti-counterfeiting, or information storage.

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