Color-adjustable photochromic ceramic as well as preparation method and application thereof

Abstract

The invention provides color-adjustable photochromic ceramic as well as a preparation method and application thereof, and belongs to the technical field of photochromic ceramic materials. The chemical formula of the color-adjustable photochromic ceramic provided by the invention is KSr2 (Nb1-xMox) 5O15 and x is more than 0% and less than or equal to 40%; a main phase of the color-adjustable photochromic ceramic is KSr2Nb5O15 which is partially doped with Mo < 6 + > and has a tetragonal tungsten bronze type structure, and a second phase of the color-adjustable photochromic ceramic is MoO3. The color-adjustable photochromic ceramic provided by the invention takes Mo < 6 + > partially doped KSN as a main phase, so that a foundation is laid for structural regulation and control of the photochromic ceramic; according to the photochromic ceramic, x is taken as a main phase, MoO3 is taken as a second phase, a competitive effect exists between the Mo6 + doped main phase and the MoO3 second phase, the color changes from a green system to a blue system along with the change of x, the photochromic performance of the photochromic ceramic can be regulated and controlled, and then the color-adjustable photochromic ceramic is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photochromic ceramic materials, and particularly relates to a color-adjustable photochromic ceramic and a preparation method and application thereof. BACKGROUND

[0002] Compared with traditional magnetic storage media, new storage materials realize information encryption storage by means of multiple functions such as light, electricity or mechanics. Among them, photochromic materials have attracted extensive attention of researchers due to their potential applications in the fields of data storage, anti-counterfeiting encryption, optical sensing and multi-color decoration. Photochromic materials can be divided into two categories: organic photochromic materials and inorganic photochromic materials. The photochromic effect of organic photochromic materials is caused by the rupture and recombination of internal chemical bonds, resulting in reversible changes in the absorption or reflection characteristics of the materials. For example: typical organic photochromic materials such as spiropyrans, azobenzene and diarylethylene. In contrast, inorganic photochromic materials have higher thermal stability and chemical stability, stronger mechanical strength and excellent fatigue resistance, and are more advantageous in the practical application of photochromic devices.

[0003] Inorganic photochromic materials include transition metal oxides, metal halides, polyoxometalate oxide ceramic materials and the like. The photochromic mechanism of inorganic materials is complex and diverse, such as electron-ion double injection model, color center model, redox model and the like. Recently, functional oxide ceramics have shown great research potential in the fields of new sensors, thin film preparation and electronics due to their high flexibility and adjustability in structure regulation and design. The color center model is the main type of photochromic mechanism in functional oxide ceramics. The color center model originates from the ion vacancy defects in functional oxide ceramics. Under ultraviolet or blue light irradiation, the carriers (electrons / holes) are excited from the valence band / conduction band and transfer across the band gap. Part of the photo-generated carriers will be captured by the defect energy level of the ion vacancy and form color centers. Then the ceramic changes to a colored state. When the colored ceramic is observed under visible light, part of the reflected light energy from the surface is absorbed by these color centers, providing enough energy to release the trapped carriers back to the conduction band / valence band. Therefore, the surface color of the irradiated photochromic ceramic changes. And this color change can be restored to the original state after thermal or light stimulation: the external stimulus provides enough energy to release the trapped carriers and destroy the photochromic color centers.

[0004] Although most of the reported functional oxide ceramics exhibit reversible and stable photochromic behavior. However, the existing inorganic photochromic materials have problems such as single color change, weak coloration contrast and the like, which limit their further development in practical applications.

[0005] In recent years, the research on the regulation of photochromic performance and multi-color control of complex oxides has found two strategies to achieve multi-color regulation of materials: (1) introducing different types of color centers in a single color center system to achieve multi-color modulation through color superposition principle; (2) based on the crystal field theory of color center light absorption behavior, regulating the local environment of color centers in the lattice to change their crystal field, and then modulating the light absorption behavior of the color centers to achieve multi-color control. The above two strategies still face great challenges in achieving multi-photochromism and multi-color control. In the process of color center regulation, the broadening of the characteristic absorption band of the color center or the splitting distribution of the absorption bands of different color centers should be avoided; otherwise, a wide spectrum of absorption will be formed in the visible light range after the material changes color, reducing the color purity.

[0006] Therefore, how to achieve controllable and efficient regulation of photochromic behavior is a technical problem to be solved in the field of photochromic ceramics. SUMMARY

[0007] The purpose of the present application is to provide a color-tunable photochromic ceramic and its preparation method and application.

[0008] In order to achieve the above-mentioned purpose of the application, the present application provides the following technical solutions: The present application provides a color-tunable photochromic ceramic, the chemical formula of which is: KSr2 (Nb 1-x Mo x )5O 15 0%<x≤40%; The main phase of the color-tunable photochromic ceramic is Mo 6+ partially doped KSr2Nb5O 15 of tetragonal tungsten bronze type structure; and the second phase of the color-tunable photochromic ceramic is MoO3.

[0009] Preferably, in the chemical formula of the color-tunable photochromic ceramic, when 0%<x≤5%, the color of the color-tunable photochromic ceramic changes from green to dark blue-gray after being irradiated by ultraviolet light.

[0010] Preferably, in the chemical formula of the color-tunable photochromic ceramic, when 5%<x≤10%, the color of the color-tunable photochromic ceramic changes from light green to khaki after being irradiated by ultraviolet light.

[0011] Preferably, in the chemical formula of the color-tunable photochromic ceramic, when 10%<x≤40%, the color of the color-tunable photochromic ceramic changes from gray-green to light blue-gray after being irradiated by ultraviolet light.

[0012] The present application also provides a preparation method of the color-tunable photochromic ceramic according to the above technical solutions, which comprises the following steps: (1) mixing SrCO3, Nb2O5, K2CO3 and MoO3, and then calcining to obtain a precursor powder; (2) mixing the precursor powder obtained in step (1) with a sintering aid and an organic binder, and then sequentially performing granulation and molding to obtain a green body; (3) sequentially performing degassing treatment and sintering on the green body obtained in step (2) to obtain a color-adjustable photochromic ceramic.

[0013] Preferably, the temperature for calcining in step (1) is 1100-1200℃; and the time for calcining is 2-4h.

[0014] Preferably, the pressure for molding in step (2) is 40-80MPa; and the pressure holding time for molding is 10-30s.

[0015] Preferably, the degassing treatment in step (3) comprises: heat preservation of the green body at a heat preservation temperature; the heat preservation temperature is 500-700℃, and the time for heat preservation is 2-6h.

[0016] Preferably, the temperature for sintering in step (3) is 1250-1350℃; and the time for sintering is 2-4h.

[0017] The application further provides an application of the color-adjustable photochromic ceramic in data storage, anti-counterfeiting encryption, optical sensing and multi-color decoration.

[0018] The application provides a color-adjustable photochromic ceramic, the chemical formula of the color-adjustable photochromic ceramic is: KSr2(Nb 1-x Mo x )5O 15 0%<x≤40%; the main phase of the color-adjustable photochromic ceramic is Mo 6+ partially doped KSr2Nb5O 15 with a tetragonal tungsten bronze structure, and the second phase is MoO3. 6+ The color-adjustable photochromic ceramic provided by the application takes Mo 15 partially doped KSr2Nb5O (KSN) as the main phase, KSN has a tetragonal tungsten bronze structure, has rich cation doping sites and various local symmetries in the crystal lattice, and lays a foundation for structural regulation of the photochromic ceramic. d Based on the band structure of KSN constructed by Nb 4 p and O 2 , partial substitution of Mo, a 3d transition metal element, can simultaneously affect the band structure and defect energy level of the KSN main body. In addition, Nb 5+ and Mo6+ The valence state difference and the ionic radius difference between Mo and Nb can also adjust the concentration of ion vacancies and their local environment (size and symmetry). Therefore, in the color-tunable photochromic ceramic provided by the present application, the introduction of Mo 6+ can effectively regulate the photochromic absorption and color change. Meanwhile, in the chemical formula of the color-tunable photochromic ceramic, MoO3 is used as the second phase, and Mo 6+ doping of the main phase competes with the MoO3 second phase. With the change of x, the photochromic performance of the photochromic ceramic can be regulated, and thus the color-tunable photochromic ceramic is obtained. The results of the examples show that, in the color-tunable photochromic ceramic provided by the present application, before and after irradiation of the irradiation light, when x = 0%, the photochromic ceramic changes from olive green to brown; when x = 5%, the green color changes to dark blue-gray; when x = 10%, the light green color changes to khaki; and when x = 40%, the gray-green color changes to light blue-gray. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 XRD patterns of the photochromic ceramics prepared in Examples 1-3 and Comparative Example 1 of the present application; Figure 2 Raman spectra of the photochromic ceramics prepared in Examples 1-3 and Comparative Example 1 of the present application; Figure 3 SEM images of the photochromic ceramics prepared in Examples 1-3 and Comparative Example 1 of the present application; Figure 4 Statistical results of the average grain size of the photochromic ceramics prepared in Examples 1-3 and Comparative Example 1 of the present application; Figure 5 SAED patterns and HR-TEM images of the photochromic ceramics prepared in Examples 1-3 and Comparative Example 1 of the present application; Figure 6 XPS patterns of the photochromic ceramics prepared in Examples 1-3 and Comparative Example 1 of the present application; Figure 7 UV-Vis diffuse reflectance spectra of the photochromic ceramics prepared in Examples 1-3 and Comparative Example 1 of the present application before and after irradiation of 360 nm light for different lengths of time (0-120 s); Figure 8 (a) photographs, (b) CIELab color coordinate diagrams, and (c) KSr2(Nb 1-x Mo x )5O 15 ceramics before and after the photochromic reaction; and Eab Figure 9 Fitted thermoluminescence spectra of the photochromic ceramics prepared in Examples 1-3 and Comparative Example 1 of the present application;​ Figure 10 Mo of photochromic ceramics prepared for the present application embodiments 1~3 and comparative example 1 6+ Schematic diagram of competition effect of substitution and MoO3 second phase formation. DETAILED DESCRIPTION

[0020] The present application provides a color-tunable photochromic ceramic, the chemical formula of which is: KSr2(Nb 1-x Mo x )5O 15 0%<x≤40%;the main phase of the color-tunable photochromic ceramic is Mo 6+ partially doped KSr2Nb5O 15 of tetragonal tungsten bronze type structure; the second phase of the color-tunable photochromic ceramic is MoO3. The color-tunable photochromic ceramic provided by the present application takes strontium potassium niobate KSN as the main phase, KSN has a tetragonal tungsten bronze type structure, has rich cation doping sites and various local symmetries in the crystal lattice, and lays a foundation for structural regulation of photochromic ceramics. The partial substitution of 3d transition metal element Mo can simultaneously affect the band structure and defect energy level of the KSN host. In addition, the valence difference and ionic radius difference between Nb 5+ and Mo 6+ can also adjust the concentration and local environment (size and symmetry) of ion vacancies. Therefore, in the color-tunable photochromic ceramic provided by the present application, the introduction of Mo 6+ can effectively regulate photochromic absorption and color change. At the same time, MoO3 is taken as the second phase in the chemical formula of the color-tunable photochromic ceramic, and there is a competition effect between the Mo 6+ doped main phase and the MoO3 second phase, which can regulate the photochromic performance of the photochromic ceramic with the change of x, and then obtain the color-tunable photochromic ceramic.

[0021] In the present application, when 0%<x≤5% in the chemical formula of the color-tunable photochromic ceramic, the color of the color-tunable photochromic ceramic under light is preferably changed from green to dark blue-gray. In the embodiments of the present application, before and after irradiation of the irradiation light, when x is 0%, the photochromic ceramic changes from olive green to brown. When x is 5%, the green color changes to dark blue-gray.

[0022] In the present application, when 5%<x≤10% in the chemical formula of the color-tunable photochromic ceramic, the color of the color-tunable photochromic ceramic under light is preferably changed from light green to khaki. In the embodiments of the present application, before and after irradiation of the irradiation light, when x is 10%, the light green color changes to khaki.

[0023] In the present application, when 10% < x ≤ 40% in the chemical formula of the color-tunable photochromic ceramic, the color of the color-tunable photochromic ceramic under light is preferably changed from greenish gray to light blue gray. In the embodiment of the present application, when x is 40% before and after irradiation of the irradiation light, the color-tunable photochromic ceramic changes from greenish gray to light blue gray.

[0024] The present application controls Mo 6+ The doped KSr2Nb5O 15 The competition mechanism between the photochromic performance of the phase and the MoO3 phase not only realizes the modulation of the color variety or the light absorption behavior, but also obtains the control of the color change of the ceramic from the green color before the color change reaction to the yellow color (5% < x ≤ 10%) and the blue color (0% < x ≤ 5%, 10% < x ≤ 40%) after the photochromic reaction.

[0025] The present application also provides a preparation method of the color-tunable photochromic ceramic according to the above technical solution, which comprises the following steps: (1) mixing SrCO3, Nb2O5, K2CO3 and MoO3, and then performing calcination to obtain a precursor powder; (2) mixing the precursor powder obtained in the step (1) with a sintering aid and an organic binder, and then sequentially performing granulation and molding to obtain a green body; (3) sequentially performing glue removal treatment and sintering on the green body obtained in the step (2) to obtain the color-tunable photochromic ceramic.

[0026] In the present application, SrCO3, Nb2O5, K2CO3 and MoO3 are mixed and then calcined to obtain a precursor powder.

[0027] The present application does not have special limitations on the sources of the SrCO3, Nb2O5, K2CO3 and MoO3, and commercially available products in the art can be used. In the present application, the purity of the SrCO3, Nb2O5, K2CO3 and MoO3 is independently preferably 99.99% or higher.

[0028] In the present application, the SrCO3, Nb2O5, K2CO3 and MoO3 are preferably mixed according to the chemical formula KSr2(Nb 1-x Mo x )5O 15 0% < x ≤ 40% in the chemical formula of the photochromic ceramic according to the above technical solution. The present application does not have special limitations on the type of the electronic balance, and an electronic balance known to those skilled in the art can be used.

[0029] In the present application, the mixing method of SrCO3, Nb2O5, K2CO3 and MoO3 is preferably first wet ball milling and first drying in sequence.

[0030] In the present application, the ball milling medium of the first wet ball milling is preferably anhydrous ethanol; the ball of the first wet ball milling is preferably agate stone. The present application does not have special limitation on the diameter of the agate stone, which can be selected by using the size of the agate stone commonly used in ball milling. In the present application, the ratio of the total mass of SrCO3, Nb2O5, K2CO3 and MoO3, the mass of the ball milling medium and the mass of the agate stone in the first wet ball milling is preferably (0.5-1.5):(1-3):(2-4), more preferably 1:2:3. In the present application, the rotation speed of the first wet ball milling is preferably 200-500 r / min, more preferably 300 r / min; the time of the first wet ball milling is preferably 6-12 h, more preferably 8-10 h. By using wet ball milling and controlling the parameters of the wet ball milling in the above range, the present application can fully mix and evenly distribute each raw material.

[0031] In the present application, the temperature of the first drying is preferably 40-60℃, more preferably 45℃; the time of the first drying is preferably 6-24 h, more preferably 12 h; the atmosphere of the first drying is preferably air. The present application does not have special limitation on the device of the first drying, which can be a conventional drying device. By drying at the above temperature and time, the present application can fully remove the ball milling medium used in the first wet ball milling.

[0032] In the present application, the temperature of the calcination is preferably 1100-1200℃, more preferably 1150-1200℃; the time of the calcination is preferably 2-3 h. By controlling the calcination temperature in the above range, the present application can promote the reaction of the raw materials to obtain the desired product crystal phase, which is more conducive to the formation of the desired crystal structure ceramic in subsequent sintering.

[0033] The present application preferably places the powder obtained after the first drying in a sealed container, and places the sealed container in a heating device for calcination. The present application does not have special limitation on the heating device, which can be a conventional heating device. In the present application, the heating device is preferably a box-type tube furnace.

[0034] After obtaining the precursor powder, the present application mixes the precursor powder with a sintering aid and an organic binder, and then sequentially performs granulation and molding to obtain a green body.

[0035] In the present application, the sintering aid preferably includes Bi2O3 or CuO. By adding the sintering aid of the above type, the present application can promote the densification of the ceramic, inhibit the grain growth, maintain the microstructure of the ceramic, reduce the sintering temperature and improve the sintering activity.

[0036] In the present application, the mass ratio of the precursor powder to the sintering aid is preferably (45-55):(1-4), more preferably 50:2. By controlling the mass ratio of the precursor powder to the sintering aid in the above range, the present application is more conducive to improving the sintering effect.

[0037] In the present application, the organic binder preferably includes a polyvinyl alcohol aqueous solution or a polyvinyl butyral ester ethanol solution. By adding the organic binder, the present application can enhance the bonding strength of the ceramic precursor powder and is conducive to subsequent removal by degreasing. In the present application, the mass concentration of the polyvinyl alcohol aqueous solution and the polyvinyl butyral ester ethanol solution is independently preferably 2-10 wt%, more preferably 5-8 wt%.

[0038] The present application does not have special limitations on the amount of the binder, which can be adjusted according to the mass of the precursor powder and the sintering aid, and can sufficiently bond the precursor powder and the sintering aid.

[0039] In the present application, the method for mixing the precursor powder, the sintering aid, and the organic binder preferably includes: sequentially performing second wet ball milling and second drying on the precursor powder and the sintering aid to obtain a mixed powder of the precursor powder and the sintering aid; and mixing the mixed powder of the precursor powder and the sintering aid with the organic binder.

[0040] The present application preferably sequentially performs second wet ball milling and second drying on the precursor powder and the sintering aid to obtain a mixed powder of the precursor powder and the sintering aid.

[0041] In the present application, the ball milling medium for the second wet ball milling is preferably anhydrous ethanol; and the balls for the second wet ball milling are preferably agate stones. The present application does not have special limitations on the diameter of the agate stones, and the size of the agate stones commonly used for ball milling can be selected. In the present application, the mass ratio of the total mass of the precursor powder and the sintering aid to the mass of the ball milling medium to the mass of the agate stones is preferably (0.5-1.5):(1-3):(2-4), more preferably 1:2:3. In the present application, the rotation speed of the second wet ball milling is preferably 200-500 r / min, more preferably 300 r / min; and the time of the second wet ball milling is preferably 6-12 h, more preferably 8-10 h. By using wet ball milling and controlling the parameters of the wet ball milling in the above range, the present application can fully mix and uniformly disperse the raw materials.

[0042] In the present application, the temperature of the second drying is preferably 40-60℃, more preferably 45℃; the time of the second drying is preferably 6-24h, more preferably 12h; and the atmosphere of the second drying is preferably air. The present application does not have special limitation on the device for the second drying, and a conventional drying device can be used. By drying at the above temperature and time, the ball milling medium used in the second wet ball milling can be removed sufficiently.

[0043] After obtaining the mixed powder of the precursor powder and the sintering aid, the present application preferably mixes the mixed powder of the precursor powder and the sintering aid with an organic binder. The present application does not have special limitation on the method for mixing the mixed powder of the precursor powder and the sintering aid with the organic binder, and the two can be mixed uniformly.

[0044] The present application does not have special limitation on the method for granulation, and a conventional granulation method can be used.

[0045] The present application preferably sieves the powder particles obtained by granulation before molding. In the present application, the particle size of the sieved powder particles is preferably 50-100 mesh. By using the powder particles with particle size of 50-100 mesh for molding, the density of the green compact can be improved more favorably.

[0046] In the present application, the molding is preferably dry pressing, the pressure of the molding is preferably 40-80MPa, more preferably 50-70MPa; and the pressure holding time of the molding is preferably 10-30s, more preferably 20-30s. The present application does not have special limitation on the size of the mold for the molding, and a conventional molding mold can be used. In the examples of the present application, the mold used for the molding is preferably a cylindrical stainless steel mold with a diameter of 12mm.

[0047] After obtaining the green compact, the present application sequentially performs degreasing treatment and sintering on the green compact to obtain the photochromic ceramic.

[0048] In the present application, the degreasing treatment preferably includes sequentially performing first heat treatment and second heat treatment on the green compact.

[0049] In the present application, the holding temperature of the first heat treatment is preferably 100-200℃, more preferably 180℃; the holding time of the first heat treatment is preferably 1-4h, more preferably 2h; the holding temperature of the second heat treatment is preferably 500-700℃, more preferably 600℃; and the holding time of the second heat treatment is preferably 2-6h, more preferably 3h. By the first heat treatment, the present application can remove the water in the green compact and dry the green compact; and by the second heat treatment, the present application can decompose the organic binder in the green compact and realize degreasing.

[0050] In the present application, the heating rate from room temperature to the soaking temperature of the first heat treatment is preferably 0.5-2℃ / min, more preferably 1℃ / min. By controlling the heating rate in the above range, the present application can slowly remove the moisture in the green body, preventing the green body from cracking.

[0051] In the present application, the heating rate from the soaking temperature of the first heat treatment to the soaking temperature of the second heat treatment is preferably 0.5-2℃ / min, more preferably 1℃ / min. By controlling the heating rate in the above range, the present application can slowly heat up, preventing the dried green body from cracking.

[0052] In the present application, the sintering temperature is preferably 1250-1350℃, more preferably 1300-1350℃; the sintering time is preferably 2-4h, more preferably 3-4h. In the sintering process of the present application, as the temperature rises, the sintering aids between the powder particles melt, forming a liquid phase environment between the powder particles, further promoting the mass transfer and growth process between the grains, promoting grain growth and densification, and forming a dense ceramic.

[0053] In the present application, the heating rate from room temperature to the sintering temperature is preferably 2-10℃ / min, more preferably 5℃ / min. By controlling the heating rate in the above range, the present application can make the reaction more complete.

[0054] In the present application, the sintering atmosphere is preferably air. The present application does not have special limitations on the sintering device, and conventional sintering devices can be used. In the embodiments of the present application, the sintering device is preferably a box-type tube furnace.

[0055] After sintering is completed, the present application preferably cools down to 500℃ at a cooling rate of 2-10℃ / min, more preferably 5℃ / min, and then cools down to room temperature with the furnace, obtaining the color-tunable photochromic ceramic.

[0056] The operation method provided by the present application can introduce Mo 6+ into the KSN ceramic through the pre-sintering and sintering method. 6+ which leads to the formation of the doped main phase and the MoO3 second phase. Moreover, there is a competitive effect between the two changes in the KSN matrix, and the introduction concentration of Mo 6+ dynamically adjusts. Thanks to the two changes, the distribution of carrier traps is optimized, and a heterojunction structure is established between the KSN and MoO3 phases.

[0057] The present application also provides the application of the color-tunable photochromic ceramic in data storage, anti-counterfeiting encryption, optical sensing, and multi-color decoration.

[0058] The application has no special limitation on the method for applying the color-adjustable photochromic ceramic to data storage, anti-counterfeiting encryption, optical sensing and multi-color decoration, and a conventional application method can be used.

[0059] In the application, since the color-adjustable photochromic ceramic is provided, it can be used for data storage, anti-counterfeiting encryption, optical sensing and multi-color decoration.

[0060] The technical solutions in the application will be clearly and completely described below in combination with the embodiments in the application. Obviously, the described embodiments are only some of the embodiments of the application, but not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0061] Embodiment 1 A color-adjustable photochromic ceramic, the chemical formula of the color-adjustable photochromic ceramic is: KSr2(Nb 1-x Mo x )5O 15 x=5%. The main phase of the color-adjustable photochromic ceramic is Mo 6+ partially doped KSr2Nb5O 15 of a tetragonal tungsten bronze type structure; and the second phase of the color-adjustable photochromic ceramic is MoO3.

[0062] The preparation method of the color-adjustable photochromic ceramic is: (1) SrCO3, Nb2O5, K2CO3 and MoO3 are weighed according to the stoichiometric ratio of KSr2(Nb 1-x Mo x )5O 15 x=5%, mixed, and then subjected to first wet ball milling and first drying, and the powder obtained by the first drying is transferred to a covered corundum crucible, placed in a high-temperature box furnace, heated from room temperature to 1100℃ at a heating rate of 5℃ / min, cooled to room temperature after calcination for 2h, and a precursor powder is obtained; wherein, the first wet ball milling is carried out in anhydrous ethanol as a medium, with agate balls, according to the mass ratio of SrCO3, Nb2O5, K2CO3 and MoO3: anhydrous ethanol: agate balls = 1:2:3, the ball milling rotation speed is 300r / min, the ball milling is carried out at room temperature in an air environment for 12h in a single direction; and the product obtained by the ball milling is dried at 45℃ in an air atmosphere for 12h; (2) The precursor powder obtained in step (1) is weighed with a sintering aid (Bi2O3) at a mass ratio of 50:2, and second wet ball milling and second drying are sequentially performed to obtain a mixed powder of the precursor powder and the sintering aid; after the mixed powder of the precursor powder and the sintering aid is mixed with an organic binder (an aqueous solution of polyvinyl alcohol with a mass concentration of 8 wt%), granulation is sequentially performed, and after the granulation is completed, 50-mesh and 100-mesh sieves are used for sieving, and powder particles between 50 and 100 meshes are selected for standby use; a cylindrical stainless steel mold with a diameter of 12 mm is used, and an appropriate amount of powder particles is weighed at a ratio of 0.5 g / piece, and then transferred into the mold, and then pressed and formed by using a hydraulic machine, the forming pressure is 40 MPa, the pressure holding time is 10 s, and after demolding, a green compact with a diameter of 12 mm and a thickness of 1 mm is obtained; The ball milling medium for the second wet ball milling is anhydrous ethanol; the balls for the second wet ball milling are agate balls, the ratio of the total mass of the precursor powder and the sintering aid to the mass of the ball milling medium and the mass of the agate balls is 1:2:3, the rotating speed of the second wet ball milling is 300 r / min; the time of the second wet ball milling is 12 h; the temperature of the second drying is 45℃; the time of the second drying is 12 h; and the atmosphere of the second drying is air; (3) The green compact obtained in step (2) is subjected to degassing treatment in an air atmosphere, heated from room temperature to 180℃ at a temperature increasing rate of 1℃ / min, and then subjected to first heat treatment at 180℃ for 2 h, and then heated from 180℃ to 600℃ at a temperature increasing rate of 1℃ / min, and then subjected to second heat treatment at 600℃ for 3 h; the degassed sample is transferred into a high-temperature box furnace, heated to 1300℃ at a temperature increasing rate of 2℃ / min in an air atmosphere, and then sintered at 1300℃ for 2 h, and then cooled to 500℃ at a rate of 5℃ / min, and then cooled to room temperature in the furnace, to obtain a color-tunable photochromic ceramic.

[0063] Example 2 A color-tunable photochromic ceramic, the chemical formula of the color-tunable photochromic ceramic is: KSr2(Nb 1-x Mo x )5O 15 x=10%; The main phase of the color-tunable photochromic ceramic is Mo 6+ partially doped KSr2Nb5O 15 ; and the second phase of the color-tunable photochromic ceramic is MoO3.

[0064] The difference between the preparation method of the color-tunable photochromic ceramic and Example 1 is that in step (1), KSr2(Nb 1-x Mo x )5O15 x=10% of stoichiometric ratio, and the remaining steps are the same as example 1.

[0065] Example 3 A color-tunable photochromic ceramic, the chemical formula of which is: KSr2(Nb 1-x Mo x )5O 15 x=40%; The main phase of the color-tunable photochromic ceramic is Mo 6+ partially doped KSr2Nb5O 15 of tetragonal tungsten bronze type structure; and the second phase of the color-tunable photochromic ceramic is MoO3.

[0066] The method for preparing the color-tunable photochromic ceramic is different from example 1 in that the raw materials are weighed according to the stoichiometric ratio of KSr2(Nb 1-x Mo x )5O 15 x=40% in step (1), and the remaining steps are the same as example 1.

[0067] Comparative Example 1 A photochromic ceramic, the chemical formula of which is: KSr2(Nb 1-x Mo x )5O 15 x=0%; The main phase of the photochromic ceramic is KSr2Nb5O 15 of tetragonal tungsten bronze type structure.

[0068] The method for preparing the photochromic ceramic is different from example 1 in that the raw materials are weighed according to the stoichiometric ratio of KSr2Nb5O 15 in step (1), and the remaining steps are the same as example 1.

[0069] Test Example (1) The phase composition and structure of the photochromic ceramics prepared in examples 1-3 and comparative example 1 were characterized by X-ray diffractometer, and the results are shown in Figure 1 From Figure 1 it can be seen that all the spectra show standard diffraction peaks of KSr2Nb5O 15 phase of tetragonal tungsten bronze type (reference JCPDS card No. 34-0123). The main diffraction peak around 31.5° corresponds to the (311) crystal plane of KSN phase, and with the increase of Mo 6+ concentration (x=0%~10%), the (311) peak shifts to high angle direction. The high angle shift of the diffraction peak indicates that part of the larger Nb 5+(r(Nb 5+ ) = 0.64 A, coordination number = 6) is replaced by smaller Mo 6+ (r(Mo 6+ ) = 0.59 A, coordination number = 6), resulting in the shrinkage of the KSN unit cell volume. In addition, from Figure 1 It can also be seen that the Mo 6+ doped samples have additional diffraction peaks, which can be attributed to the generated MoO3 second phase (referring to JCPDS card No. 21-0569), and the diffraction peaks around 26° and 29° are particularly obvious, containing the main and secondary diffraction peaks of the MoO3 phase. The diffraction intensity of these two peaks increases with the increase of Mo 6+ concentration, indicating that the content of the MoO3 second phase increases with the increase of Mo 6+ doping amount. The above XRD analysis results show that the Mo 6+ doped KSN-based ceramic produces a synergistic effect of unequal ion substitution and double-phase composition.

[0070] (2) The vibration mode of chemical bonds in the photochromic ceramic prepared in Examples 1-3 and Comparative Example 1 was detected by a microscopic confocal Raman spectrometer, and the Raman spectrum is shown in Figure 2 From Figure 2 it can be seen that in the range of 100-800 cm -1 , the peak near 260 cm -1 and the peak of 600-620 cm -1 correspond to the characteristic vibration peaks of the O-Nb-O bending vibration mode T 2g and the Nb-O stretching vibration mode A 1g of the NbO6 octahedron in the KSN lattice. After Mo 6+ doping, the wave number of the T 2g mode increases, indicating that Mo 6+ has a substitution effect on Nb 5+ . In addition, when the Mo 6+ concentration increases to 40%, an additional vibration signal peak appears at 335 cm -1 , which corresponds to the O-Mo-O bending vibration of MoO3 in the low frequency band of 300-500 cm -1 . Therefore, the vibration characteristics of the Raman spectrum also confirm the synergistic effect of the substitution effect and the composite effect after Mo 6+ doping.

[0071] (3) The microstructure of the photochromic ceramic prepared in Examples 1-3 and Comparative Example 1 was observed by a field emission scanning electron microscope (FE-SEM), and the SEM image is shown in Figure 3 , and the average grain size statistical results are shown in Figure 4As shown. Before FE-SEM observation, the carefully polished photochromic ceramic surface was thermally etched at 1200°C for 15 min to promote the exposure of grain boundaries. From Figure 3 and 4 It can be seen that when x As the value increased from 0% to 10%, the average grain size gradually increased from 2.03 μm to 8.23 ​​μm, while the grains maintained an amorphous morphology. Furthermore, the degree of densification in the microstructure exhibited certain changes, with pure KSN ceramics ( x =0%) has a small amount of porosity, Mo 6+ After doping ( x =5%), with a significant increase in porosity. Further, Mo 6+ Increasing the concentration to 10% promotes grain growth and sintering, resulting in almost imperceptible porosity in the microstructure. When Mo... 6+ When the concentration was further increased to 40%, the average grain size decreased to 1.23 μm, and some platy particles appeared. The grain diameter of the platy particles was approximately 1 μm, and the thickness was 0.1–0.2 μm. This specific grain morphology may correspond to the second phase of MoO3. Combining the results of X-ray diffraction and Raman spectroscopy, the change in microstructure can be attributed to the different Mo concentrations introduced. 6+ The combined effect of doping and MoO3 recombination. When x =5%, at a lower Mo 6+ At the introduced concentration, Nb in the KSN lattice 5+ Moped 6+ Substitution is dominant; this unequal substitution leads to lattice distortion, inhibiting the grain growth and densification processes in ceramics. When x When =10%, some of the introduced Mo 6+ A reaction occurs, generating a second MoO3 phase, which precipitates in the interstitial spaces or interfaces of KSN grains. Due to its low melting point (approximately 795°C), the generated MoO3 second phase acts as a sintering aid during high-temperature sintering, providing a liquid environment between KSN grains, effectively promoting mass transfer and grain growth, and driving the densification of the ceramic. With the increasing activity of Mo... 6+ Further increase in concentration ( x (40%) The excess MoO3 second phase was not completely consumed as a sintering aid during the sintering process, and the residual MoO3 content reached the level of the KSN phase. The sintering characteristics of the composite ceramic were significantly affected by the MoO3 phase. Therefore, densification of the ceramic could not be achieved under the initial sintering conditions, and lamellar MoO3 particles were easily observed in the microstructure.

[0072] (4) In order to study Mo 6+The effect of doping on the crystal structure, and the effect on the photochromic ceramic KSr2(Nb) prepared in Examples 1-3 and Comparative Example 1. 1-x Mo x 5O 15 The selected electron diffraction patterns and high-resolution transmission electron microscopy images were characterized, and the results are as follows: Figure 5 As shown. Figure 5 (a1) to 5 (d1) show respectively x =0% (along [ ] T zone axis) x =5% (along [ 20] T zone axis) x =10% (along [1] 6] T zone axis) and x =40% (along [ ] T Selected area electron diffraction (SAED) pattern of the zone axis. Figure 5 From (a1) to 5(d1), it can be seen that Mo 6+ After doping ( x (>0%) Some superlattice diffraction points appeared, which maintained a different periodic structure from the diffraction matrix of the KSN lattice. For the tungsten bronze type structure, the periodic superlattice reflects the octahedron in... ab Out-of-plane tilt, through the periodic difference between the superlattice and the main diffraction matrix, these structural modulations can be divided into two types: commensurable / incommensurable modulation refers to the situation in reciprocal space where the wave vector of the superlattice can / cannot be converted into a simple integer multiple of the wave vector of the main lattice. The wave vector of the incommensurable superlattice is calculated using equations (1) and (2): Equation (1) Equation (2) In equation (1), a 0 * , b 0 * and c 0 * For reciprocal space vectors; in equations (1) and (2), δ This indicates the periodic deviation from the comparability structure. x and y These represent the distances between the main diffraction spot and two adjacent superlattice spots, respectively. Based on this, x =5%, 10% and 40% of the samples δ The values ​​were 0.371, 0.02, and 0.136, respectively.

[0073] Figure 5(a2) 5 (d2) is KSr2(Nb 1-x Mo x )5O 15 High-resolution transmission electron microscopy (HR-TEM) images of the ceramics. The lattice spacing of all samples has been calibrated and labeled in each image. According to the interplanar spacing formula of tetragonal structure, Mo 6+ substitution slightly shrinks the lattice parameters along a and c directions. Combined with the results of selected area electron diffraction (SAED) and HR-TEM, it can be known that Mo 6+ substitution affects the unit cell size and octahedral structure of KSN lattice, and further changes the local environment (including size and symmetry) around the color center in the lattice. The regulation of the local environment of the color center can modulate the transition behavior and energy level degeneracy of the photo-generated carriers, so as to realize the adjustment of the photochromic absorption peak center position and bandwidth.

[0074] (5) The influence of Mo 6+ substitution on the chemical state of elements in the photochromic ceramics prepared in Examples 1-3 and Comparative Example 1 was studied by XPS spectrum. Figure 6 (a) shows the wide scan XPS spectra of KSr2(Nb 1-x Mo x )5O 15 ceramics in the range of 0-1200 eV. The characteristic peaks of K, Sr, Nb and O elements can be well indexed in all samples. Figure 6 (b) shows the narrow scan XPS Nb 3 d spectra of all samples. No additional sub-peaks appear in all spectra. However, with the increase of Mo 6+ concentration, the peak position gradually moves to the high binding energy direction, indicating that the electron cloud density around the Nb element gradually decreases with the increase of Mo 6+ doping amount. Since the oxygen vacancy is the main photochromic color center in KSN-based ceramics, the narrow scan XPS O 1 s spectra of all samples were detected and fitted by Gaussian deconvolution method, as shown in Figure 6 (c). The O 1 s peak can be divided into three sub-peaks with different binding energies (centered at 529 eV, 531 eV and 533 eV): (1) the sub-peak with lower binding energy (blue, labeled as O L ) is related to lattice oxygen, (2) the sub-peak with medium binding energy (pink, labeled as O C ) corresponds to chemisorbed oxygen such as oxygen vacancy, and (3) the sub-peak with higher binding energy (green, labeled as O P ) corresponds to physisorbed oxygen such as O2. Figure 6 (d) shows the O 1s Area ratio between three sub-peaks of the spectrum, where O C The area ratio of the sub-peaks can be used to qualitatively assess the oxygen vacancy content in the material. The pure KSN lattice contains some oxygen vacancies generated during the high-temperature sintering process. In the low Mo 6+ doping concentration (x x =5%), the donor doping suppresses the generation of oxygen vacancies. With the increase of Mo 6+ concentration, some MoO3 secondary phase is generated and precipitates from the KSN phase, and the suppression of oxygen vacancies is also weakened, x =10% sample retains more oxygen vacancies in the KSN lattice. After further increasing the Mo 6+ concentration, more MoO3 secondary phase is formed, and the substitution of Mo 6+ is further reduced, x =40% sample, the area ratio of O C sub-peak is lower than that of the x =10% sample.

[0075] In addition, Figure 6 (e) are the Mo 3 x doping concentration of 5%, 10% and 40% samples, respectively. d Narrow scan XPS spectra of Mo 3 Figure 6 From (e), it can be seen that there is a competition effect between the main phase of Mo 6+ doping and the generation of MoO3 secondary phase. At low doping concentration (x x =5%), although there is a noise signal, the characteristic XPS peak of Mo element can still be identified, which corresponds to a small amount of Mo 6+ substitution in the KSN lattice. For the x =40% sample, the characteristic XPS peak of Mo 3 d is smooth and clear, which is related to the high concentration of Mo element brought by the MoO3 secondary phase. x The spectrum of the 6+ =10% sample is almost free of Mo element characteristic XPS signal, reflecting the coexistence state of Mo 6+ substitution and MoO3 secondary phase generation. The competition effect of the two processes leads to a lower Mo 6+ doping concentration in the KSN lattice and a lower MoO3 secondary phase content in the ceramic, so x =10% sample, the Mo 3 d signal is difficult to detect.

[0076] (6) The photochromic performance of the photochromic ceramics prepared in Examples 1-3 and Comparative Example 1 was evaluated by measuring the reflectivity change before and after 365 nm light irradiation. Figure 7 (a)~7 (d) are KSr2(Nb 1-x Mo x )5O15 UV-Vis diffuse reflectance spectra of ceramics before and after irradiation with 365nm light for different durations (0s~120s). Figure 7 It can be seen that after irradiation with 365nm light, the reflectivity of all samples in the wavelength range of 380~800nm ​​gradually decreased with the extension of irradiation time, and the color of the ceramic surface darkened synchronously (see...). Figure 7 (Illustrations (a) to 7 (d)). All stained samples were completely decolorized and restored to their initial state after heating at 200°C for 30 minutes.

[0077] According to the color center theory, the changes in the reflectivity and surface color of a sample originate from the generation of photochromic color centers during irradiation. Cations or ion vacancies in the material form trap energy levels in the band gap. Irradiation with 365nm light can excite valence band electrons to jump across the band gap and enter the conduction band; some excited charge carriers are captured by defect energy levels during migration, thus forming photochromic color centers. When the irradiated sample is placed under visible light, these color centers absorb some visible light, providing release energy for the captured charge carriers to return to the conduction band. The reflected light energy of the irradiated sample decreases, and the surface color also changes. Therefore, the photochromic properties and color changes are closely related to the characteristic absorption of the photochromic color centers. The photochromic absorption behavior can be quantitatively evaluated by calculating its absorption spectrum using the following formula (3): Equation (3) Where ∆ R t Indicates irradiation with 365nm light t After s, in λ Photochromic contrast (reflectance change) at a wavelength of nm. R 0 ( λ )and R t ( λ (365nm light irradiance) t Before and after s λ Reflectance at nm wavelength. Photochromic absorption spectra of all samples (irradiated for 60 s) are as follows. Figure 7 As shown in (e). Furthermore, Figure 7 (f) shows the curves of maximum photochromic contrast ratio as a function of irradiation time for all samples. Figure 7 (f) It can be seen that all samples exhibit an exponential function trend: x The photochromic contrast of samples with concentrations of 0%, 5%, and 10% reached saturation after 60 seconds of irradiation; while x =40% of the samples showed further improvement in contrast after the irradiation time was extended to 120s, and their photochromic response rate was the lowest among all samples.

[0078] Pure KSN ceramics have a broad absorption band (400~800nm), with the absorption peak centered at around 520nm, and a maximum photochromic contrast of approximately 15%. Mo 6+ After doping, the maximum photochromic contrast ratio increased to 24%, which is mainly attributed to Mo. 6+ The donor doping effect. Although oxygen vacancies are the main color centers in KSNs, their defect energy level distribution also affects photochromic performance. Based on color center theory, traps in materials can be classified into three categories according to energy depth: shallow traps, active traps, and deep traps. Deep traps have a large energy difference from the conduction band, and the energy required to release the trapped carriers is much higher than that provided by visible light or thermal stimulation. Therefore, deep traps in KSNs usually do not participate in the photochromic reaction. For x =5% of the sample, Mo 6+ Donor doping suppresses oxygen vacancy formation and also modulates the distribution of oxygen vacancy defect energy levels in KSN and reduces their energy depth. Therefore, low concentrations of Mo... 6+ It can suppress the formation of deep traps and improve the efficiency of oxygen vacancies in the photochromic reaction. Further improve Mo... 6+ concentration( x =10%) will promote the formation of the second phase of MoO3. Because Mo 6+ There is a competitive effect between the formation of the doped main phase and the second phase of MoO3. x The increased oxygen vacancies and deeper defect energy level distribution in the 10% sample resulted in a decreased carrier trapping efficiency, thus reducing its maximum photochromic contrast to 7.5%, even lower than that of pure KSN ceramics. When Mo... 6+ When the concentration is increased to 40%, more MoO3 second phase is generated in the ceramic, and at this time the photochromic properties of the sample are mainly affected by the MoO3 phase. x =40% of the samples exhibited greater photochromic contrast (>30%) and longer saturation time than other samples, which is consistent with the photochromic characteristics of transition metal oxides.

[0079] (7) In addition to photochromic contrast, color change is another core property of photochromic materials. Figure 8 (a) Photographs of the photochromic ceramic samples prepared in Examples 1-3 and Comparative Example 1 before and after the photochromic reaction are shown. For ease of comparison, all samples were half-covered with aluminum foil, leaving the other half exposed to irradiation. Therefore, the left side of all samples is the original part, and the right side is the colored part. As can be seen from the magnified photographs, the color changes of all samples are different: (1) x =0%, olive green turns brown; (2) x =5%, green turns into dark blue-gray; (3) x =10%, light green turns khaki; (4) x=40%, gray-green turned into light blue-gray.

[0080] To quantitatively evaluate the color changes of all samples before and after the photochromic reaction, the CIE Lab color coordinates of the photochromic ceramics prepared in Examples 1-3 and Comparative Example 1 were measured using a commercial colorimeter. The CIE Lab color coordinates include three parameters: L The coordinates represent brightness. a The coordinates cover a color range from dark green to gray to bright pink. b The coordinates reflect the color range from bright blue to gray to yellow. Figure 8 (b) provided respectively a x b Color gamut and L Color bars are used to show the changes in color and brightness after the photochromic reaction. Cycles and dots represent the coordinates of the samples before and after the photochromic reaction (irradiation with 365 nm light for 60 s), respectively. Figure 8 As shown in (b), x =5%, 10% and 40% of the samples in a x b The color gamut exhibits obvious color variations, among which x =40% of the samples showed greater brightness variation than other samples. Total color difference ΔEab The difference between the two color states is used to evaluate the difference, and it is calculated according to equation (4): Equation (4) in ∆L , ∆a and ∆b This represents the coordinate difference between the color states before and after the photochromic reaction. Calculations for all samples. ∆ Eab Values ​​such as Figure 8 As shown in (c). Due to the presence of two different photochromic phases in the ceramic, x =40% (22.5%) of the samples showed a larger ΔEab Value. It is worth noting that, x =5% (16.5) of the sample ΔEab Value higher than x =0% (7.5) of the sample, which indicates that Mo 6+ The substitution modulates the local environment around the color center in the KSN lattice through structural modulation, thereby controlling the carrier migration behavior, photochromic absorption characteristics, and color changes.

[0081] (8) The distribution of carrier traps in the material affects the photochromic properties of the sample. To further investigate Mo... 6+ The effect of the introduction of [a specific element] on the trap was measured by measuring the coloring of KSr2 (Nb). 1-x Mo x 5O 15Thermoluminescence (TL) spectra of the ceramics. As shown in Fig. 1, Figure 9 Based on the color center theory, the TL spectra can be fitted as a number of sub-peaks with different center temperatures, which represent the carrier traps with different energy depths. For the sample with x =0%, the TL spectra can be divided into three sub-peaks with center temperatures of about 323 K, 348 K and 385 K, respectively, corresponding to the shallow traps (ST), active traps (AT) and deep traps (DT) in the band gap of KSN phase. Mo 6+ After Mo x =5%, Figure 9 (b), both the spectra and the sub-peaks change significantly: an additional sub-peak with a higher center temperature (more than 550 K) appears, and the center temperatures of the AT and DT sub-peaks also change. More importantly, the relative area ratio of the AT sub-peak increases significantly. For inorganic photochromic materials, the active traps are the main color centers in the photochromic reaction, because the defect energy levels have a suitable energy depth, and the photo-generated carriers can be stably and reversibly captured and released by the active traps. Therefore, Mo 6+ substitution promotes the formation of more active traps in the KSN matrix, thereby enhancing the photochromic contrast. In addition, the change in the center temperatures of the AT and DT sub-peaks may be due to the potential generation of MoO3 secondary phase, which has a different band structure and photochromic properties from the KSN phase.

[0082] For the sample with x =10%, Mo 6+ substitution and the competition effect between MoO3 secondary phase generation result in the generation of more deep traps (larger area ratio of DT sub-peak, as shown in Fig. 1 Figure 9 (c)), which reduces the carrier trap efficiency in the photochromic reaction, thereby reducing the photochromic contrast.

[0083] With the further increase of Mo 6+ concentration ( x =40%), the content of the generated MoO3 phase reaches the KSN phase, and the contribution of the MoO3 phase carrier trap gradually increases, resulting in a larger area ratio and an increase in the center temperature of the AT sub-peak, as shown in Fig. 1 Figure 9 (d).

[0084] (9) Based on the results of the microstructure and photochromic performance, Figure 10 the potential mechanism of Mo 6+ doping on KSN-based ceramics is summarized. The introduction of Mo 6+ mainly produces two effects: one is Mo 6+ substitution for Nb 5+ (forming Mo Nb defects) in the KSN lattice, and the other is the precipitation of MoO3 secondary phase from the KSN matrix.

[0085] For Mo 6+ The substitution effect, due to Mo 6+ With Nb 5+ The differences in ionic radii lead to shrinkage of the KSN unit cell volume (XRD results); simultaneously, donor doping causes distortion and tilting of the octahedrons (SAED results). These lattice changes alter the local environment of the photochromic color centers (vacancy defects), which, according to crystal field theory, modulate the energy level degeneracy and distribution state, ultimately enabling the control of the photochromic properties of the KSN phase.

[0086] Regarding the effect of the MoO3 second phase, its formation process competes with the KSN phase for oxygen, resulting in a heterojunction between the two phases. Therefore, the formation of the MoO3 second phase exacerbates the oxygen vacancies (V0.05) in the KSN lattice. O ·· The formation of the heterojunction interface enhances the distribution of related defect energy levels within the bandgap. Furthermore, as a transition metal oxide, the MoO3 second phase is itself a photochromic material, and its photochromic absorption characteristics differ from those of the KSN matrix. The bandgap values ​​of the KSN matrix and the MoO3 phase are approximately 3.40 eV and 2.49 eV, respectively, while their valence band maximum values ​​are approximately -0.47 eV and -0.10 eV, respectively. These differences in band structure between the KSN and MoO3 phases promote the formation of the type I heterojunction interface. The construction of the heterojunction may induce new carrier transition pathways and alter its photochromic absorption behavior.

[0087] In this invention, Mo 6+ There is a competitive effect between the doped main phase and the formation of the MoO3 second phase. 6+ Increased concentration affects the outcome of this competitive effect. When Mo 6+ Low concentration ( x = 5%), Mo 6+ The substitution effect prevails. And when Mo 6+ High concentration ( x When the content of the second phase of MoO3 is 40%, the second phase of MoO3 plays a major role. x = 10% of the samples are close to the equilibrium point of the competitive effect, resulting in low photochromic contrast.

[0088] As can be seen from the above results, the present invention will use Mo 6+ Introducing KSr2Nb5O 15 In ceramics, the effects of [the study] on microstructure and photochromic properties were systematically investigated. X-ray diffraction (XRD) patterns and Raman spectroscopy results showed that, except for Mo [the ceramics], [the ceramics exhibited certain properties]. 6+ Partially replaces Nb 5+ In addition, a second phase of MoO3 was generated at the reduction site during the reaction, and its content increased with the amount of Mo.6+ The concentration increases with increasing concentration. Mo 6+ The method replaces and suppresses the generation of oxygen vacancies and optimizes the trapping distribution of oxygen vacancies, thereby improving the trapping efficiency of oxygen vacancies in the KSN matrix and enhancing the photochromic contrast. ∆R The value increased significantly from 15% to 24%. Furthermore, Mo... 6+ There is a competitive effect between the formation of the doped main phase and the formation of the MoO3 second phase. When Mo 6+ High concentration ( x When the concentration of KSN is 40%, the formation of the second phase of MoO3 is dominant. As another photochromic phase, the MoO3 phase, by constructing a heterojunction interface between KSN and the MoO3 phase, not only improves the photochromic contrast but also significantly modulates the color change. The total color difference after the photochromic reaction... ΔEab Value from 7.5 ( x =0%) increased to 22.5 ( x =40%). This invention proposes a method utilizing Mo 6+ A novel strategy for dynamically regulating the photochromic properties of KSN-based ceramics through the competitive effect of doping and the formation of the MoO3 phase.

[0089] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A color-tunable photochromic ceramic, wherein the chemical formula of the color-tunable photochromic ceramic is: KSr2(Nb 1-x Mo x 5O 15 0% < x ≤ 40%; The main phase of the color-tunable photochromic ceramic is Mo. 6+ Partially doped tetragonal tungsten bronze-type KSr2Nb5O 15 The second phase of the color-tunable photochromic ceramic is MoO3.

2. The color-tunable photochromic ceramic according to claim 1, characterized in that, In the chemical formula of the color-tunable photochromic ceramic, when 0% < x ≤ 5%, the color of the color-tunable photochromic ceramic changes from green to dark blue-gray after being irradiated with ultraviolet light.

3. The color-tunable photochromic ceramic according to claim 1, characterized in that, In the chemical formula of the color-tunable photochromic ceramic, when 5% < x ≤ 10%, the color of the color-tunable photochromic ceramic changes from light green to khaki after being irradiated with ultraviolet light.

4. The color-tunable photochromic ceramic according to claim 1, characterized in that, In the chemical formula of the color-tunable photochromic ceramic, when 10% < x ≤ 40%, the color of the color-tunable photochromic ceramic changes from gray-green to light blue-gray after being irradiated with ultraviolet light.

5. A method for preparing color-tunable photochromic ceramics according to any one of claims 1 to 4, comprising the following steps: (1) SrCO3, Nb2O5, K2CO3 and MoO3 were mixed and then calcined to obtain precursor powder; (2) After mixing the precursor powder obtained in step (1) with the sintering aid and the organic binder, the mixture is granulated and formed in sequence to obtain a green body; (3) The green body obtained in step (2) is subjected to debinding and sintering in sequence to obtain color-adjustable photochromic ceramic.

6. The preparation method according to claim 5, characterized in that, The roasting temperature in step (1) is 1100~1200℃; the roasting time is 2~4h.

7. The preparation method according to claim 5, characterized in that, The molding pressure in step (2) is 40~80MPa; the molding holding time is 10~30s.

8. The preparation method according to claim 5, characterized in that, The glue removal process in step (3) includes: keeping the green body at a heat preservation temperature of 500~700℃ and the heat preservation time of 2~6h.

9. The preparation method according to claim 5, characterized in that, The sintering temperature in step (3) is 1250~1350℃; the sintering time is 2~4h.

10. The application of the color-tunable photochromic ceramic as described in any one of claims 1 to 4, or the color-tunable photochromic ceramic prepared by any one of claims 5 to 9, in data storage, anti-counterfeiting encryption, optical sensing, and multi-color decoration.

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