Rare earth doped perovskite type high-entropy fluorescent ceramic powder as well as preparation and application thereof

Abstract

The invention belongs to the field of inorganic luminescent materials, and particularly relates to rare earth doped perovskite type high-entropy fluorescent ceramic powder as well as a preparation method and application thereof. The chemical general formula of the material is A1-xLnxBO3, wherein the A site is composed of five metal ions, namely Ca < 2 + >, Sr < 2 + >, Ba < 2 + >, La < 3 + > and Na < + >, in an equal molar ratio; b is one or five metal ions selected from Ti < 4 + >, Zr < 4 + >, Sn < 4 + >, Ge < 4 + >, Hf < 4 + > and Se < 4 + >; ln is one or more of Eu < 3 + >, Er < 3 + >, Sm < 3 + >, Pr < 3 + >, Dy < 3 + > and other rare earth ions, and the value range of the doping concentration x is 0 < x < = 0.10. The rare earth doped perovskite type high-entropy fluorescent ceramic powder is prepared by adopting a sol-gel synthesis technology. Compared with traditional fluorescent ceramic powder with single-component SrTiO3 as a matrix, the fluorescent ceramic powder has the advantages that the fluorescence intensity is improved by about 6 times, the thermal stability is obviously improved, and the color purity is as high as 98.5%. The material has important application in the fields of high-end solid-state illumination, full-spectrum display devices and fluorescence sensing.

Description

Technical Field

[0001] The present invention relates to luminescent ceramic materials and their preparation and applications, specifically to rare-earth doped perovskite-type high-entropy oxide fluorescent ceramic powders and their preparation and applications, belonging to the fields of inorganic luminescent materials and high-entropy ceramics. Background Art

[0002] In recent years, with the rapid development of fields such as solid-state lighting, display technology, and optical sensing, rare-earth doped fluorescent materials have attracted much attention as key optical functional media. Traditional fluorescent materials usually use single-component oxides as matrices, and the luminescence is regulated by doping rare-earth ions. However, limited by the limitations of the crystal field environment of the matrix materials, there are some problems with current rare-earth fluorescent powders, such as high local symmetry of rare-earth ions, low luminescence intensity and quantum efficiency; at high temperatures, the lattice rigidity decreases, non-radiative transitions dominate, resulting in severe thermal quenching and poor thermal stability; the spectral regulation ability is limited, and the color purity is relatively low, making it difficult to meet the requirements of high-end display devices for wide color gamuts, which restricts the application of rare-earth luminescent materials, and new suitable matrix materials need to be found.

[0003] Following high-entropy alloys, high entropy was first introduced into ceramics in 2015. As a new type of multi-principal element material system, high-entropy ceramics show unique high-entropy stabilization effects and lattice distortion characteristics through the solid solution of equimolar ratios of more than five components in a single lattice. Research shows that the strong lattice stress in high-entropy ceramics can effectively reduce the local symmetry of activator ions (rare-earth ions), enhance their dipole transition probability, and make their luminescence performance superior to that of traditional single-component fluorescent matrix materials. CN115304373 A discloses a B-site penta-high-entropy perovskite fluorescent ceramic Ca 0.98 Sm 0.02 (Sn 0.2 Zr 0.2 Hf 0.2 Ti 0.2 Nb 0.2 )O3, whose luminescence intensity and fluorescence lifetime are both improved compared with traditional single-component systems; CN117903799 A uses solution combustion method and high-temperature calcination method to prepare Ce 0.2 La 0.2 Gd 0.2 Y 0.2 Lu 0.2 O 1.6 :12mol%Eu 3+ high-entropy fluorescent materials, and compare them with the blank sample ceramic CeO2:12mol%Eu 3+ to prove that high-entropy fluorescent ceramics can greatly enhance the luminescence performance and increase the quantum yield, and have good application prospects in the field of light-emitting diodes.

[0004] Compared with traditional single-component ceramics, high-entropy ceramics have more excellent properties in terms of mechanics, thermotics, optics, etc. However, at present, the optical properties of high-entropy ceramics have been less developed, and their luminescence properties need to be improved. Moreover, at present, the preparation process of high-entropy fluorescent ceramics mostly adopts the high-temperature solid-phase method, resulting in relatively serious component segregation and high grain boundary defect density, significantly deteriorating the luminescence properties. Therefore, it is of great significance to develop a high-entropy perovskite fluorescent ceramic with both high lattice distortion energy, atomic-level doping uniformity and excellent luminescence characteristics. Summary of the Invention

[0005] The purpose of the present invention is to improve the luminescence properties of high-entropy fluorescent ceramics with a high-entropy ceramic with macroscopic lattice stability and large microscopic distortion as the matrix and rare-earth ions as the activation center by using a wet chemical method, and then provide a preparation method and application of rare-earth doped perovskite-type high-entropy oxide fluorescent ceramics.

[0006] In order to achieve the above purpose, the technical solution provided by the present invention is:

[0007] A rare-earth doped perovskite-type high-entropy oxide fluorescent ceramic powder, characterized in that its chemical formula is A 1- x Ln x BO3, where the A-site is composed of Ca 2+ , Sr 2+ , Ba 2+ , La 3+ , Na + five cations in equimolar ratio; the B-site is composed of Ti 4+ , Zr 4+ , Sn 4 + , Ge 4+ , Hf 4+ , Se 4+ one or five cations in equimolar ratio, Ln is Eu 3+ , Er 3+ , Sm 3+ , Pr 3+ , Tm 3+ , Dy 3 + one or more of them, and the doping concentration x ranges from 0 < x ≤ 0.10.

[0008] The rare-earth doped perovskite-type high-entropy oxide fluorescent ceramic powder, its chemical formula is A 1-x Ln x BO3, where the A-site is composed of Ca 2+ , Sr 2+ , Ba 2+ , La 3+ , Na +The five cations in it are composed in equimolar ratio, and the B-site is Ti 4+ , Zr 4+ , Sn 4+ , Ge 4+ , Se 4+ One or more of the cations in it are composed in equimolar ratio.

[0009] The rare earth doped perovskite type high entropy oxide fluorescent ceramic powder described above has the chemical formula A 1-x Ln x BO3. When the A-site is Ca 2+ or Sr 2+ , and the B-site is Ti 4+ , Zr 4+ , Sn 4+ , Ge 4+ , Se 4+ The five cations are composed in equimolar ratio.

[0010] The preparation method of the rare earth doped perovskite type high entropy oxide fluorescent ceramic powder includes the following steps:

[0011] Step (1): Weigh the raw materials of Ca 2+ , Sr 2+ , Ba 2+ , La 3+ , Na + in equimolar ratio, and add the Ln raw material to dissolve in the solvent. Add the raw materials of one or equimolar ratio of multiple kinds with the B-site being Ti 4+ , Zr 4+ , Sn 4+ , Ge 4+ , Se 4+ in one or more kinds according to the element molar ratio in the chemical formula, and stir and dissolve fully to obtain a sol; the solvent is any two or more of deionized water, acetic acid, absolute ethanol, and methanol;

[0012] Step (2): Perform preliminary drying, dry gel, and grinding on the obtained sol to obtain a powder;

[0013] Step (3): Calcinate the obtained powder at high temperature to obtain a rare earth ion doped perovskite type high entropy oxide fluorescent ceramic powder.

[0014] The preparation method of the rare earth doped perovskite type high entropy oxide fluorescent ceramic powder includes the following steps:

[0015] Step (1): When the A-site is Ca 2+ or Sr 2+ , weigh one or two kinds of the above raw materials in equimolar ratio, and add the Ln raw material to dissolve in the solvent; weigh Ti 4+、Zr 4+ Sn 4+ ,Ge 4+ 、Se 4+ The raw materials are added with a stabilizer, stirred and dissolved to obtain a sol; the solvent is any two or more of deionized water, acetic acid, anhydrous ethanol, and methanol. The stabilizer is polyethanol or polyvinyl pyrrolidone;

[0016] Step (2): preliminarily drying, drying and grinding the sol to obtain powder;

[0017] Step (3): calcining the powder at high temperature to obtain rare earth ion-doped perovskite-type high entropy oxide fluorescent ceramic powder.

[0018] Preferably, the raw material used for the A-position element is a soluble metal salt, and one or more soluble salts such as acetate, nitrate, carbonate or hydrochloride can be selected, and the color is white or light color to avoid the influence of black / dark color on the luminescent color.

[0019] Preferably, the raw material used for the A-site element is a soluble metal salt, preferably acetate, nitrate or carbonate.

[0020] Preferably, the raw material used for the B-site element can be a soluble metal salt or metal oxide, which is white or light in color; the raw material used for the B-site element can be one or more of a soluble alcohol salt, acetate, nitrate, carbonate, hydrochloride or metal oxide.

[0021] Preferably, the method for preliminary drying in step (2) is to control the temperature at 25-50°C and volatilize the solvent for 12-48 hours; the dry glue treatment method is to dry at 100-150°C for 12-72 hours; the heating rate for calcination in step (3) is 5-10°C / min, heating to 500-600°C, keeping warm for 2h-6h, then heating to 800-1000°C at a heating rate of 5-10°C / min, keeping warm for 2h-6h, and finally heating to 1200-1400°C at a heating rate of 2-6°C / min, keeping warm for 2-5h.

[0022] The rare earth doped perovskite type high entropy oxide fluorescent ceramic is used in the fields of lighting, transportation, military, decoration, biomedicine, display imaging and other luminescent materials.

[0023] Beneficial effects of the present invention:

[0024] 1. The present invention provides a rare earth doped perovskite type high entropy fluorescent ceramic powder prepared by a sol-gel method, which is composed of five elements at the A position in equal moles to form a chemical formula of (Ca 0.2 Sr 0.2 Ba0.2 La 0.2 Na 0.2 ) 1-x Ln x A single-phase solid solution of BO3. It is composed of equimolar amounts of five elements at the B-site, forming a chemical formula of A 1-x Eu x (Zr 0.2 Ti 0.2 Sn 0.2 Ge 0.2 Se 0.2 )TiO3. Compared with the traditional single-component system, due to the introduction of different component cations, there are radius differences, and different components interact with each other, resulting in large lattice distortion and stress fields inside the ceramic, leading to a decrease in the local symmetry of rare-earth ions, thus significantly improving the luminescence intensity, thermal stability, and quantum efficiency.

[0025] 2. The (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 1-x Eu x TiO3 and Sr 1-x Eu x (Zr 0.2 Ti 0.2 Sn 0.2 Ge 0.2 Se 0.2 )TiO3 phosphor prepared by the present invention emits characteristic red light of Eu 3+ under the excitation of 465 nm blue light. Currently, commercial white light is composed of InGaN blue chips and yellow phosphor YAG. Due to the lack of red light in the emitted light, after long-term use, the final mixed light emitted will be bluish, and blue light is extremely harmful to the human eye. The solution is to add red phosphor. The Eu 3+ -doped perovskite-type high-entropy oxide ceramics prepared by the present invention can effectively absorb blue light and convert it into red light, and can be used to supplement red light in white light to improve the color rendering index and enhance stability.

[0026] 3. The sol-gel method adopted by the present invention to prepare high-entropy fluorescent ceramic powders has relatively more uniform sample particle sizes and higher dispersibility. By fully dissolving the selected soluble metal salts with solvents and stabilizers, a homogeneous and stable sol is obtained. The operation is simple. After preliminary drying treatment, drying is carried out to ensure complete removal of the solvent. The selected calcination time and temperature can weaken the agglomeration phenomenon of the powders, improve their crystallinity, and are beneficial to obtaining a single-phase material.

[0027] 4. The synthesis method of the rare earth-doped perovskite-type high-entropy ceramic powder prepared by the present invention is simple, highly reproducible, low-cost, green and environmentally friendly, etc. Moreover, the product has the advantages of single phase, uniform element distribution, high fluorescence intensity, high quantum yield, high thermal stability, etc., and has potential application value in the fields of lighting, display, anti-counterfeiting, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The following further describes in detail the specific embodiments of the present invention with reference to the drawings.

[0029] Figure 1 X-ray diffraction pattern of (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 1-x Eu x TiO3 (x = 0.06 - 0.10) prepared in Example 1 of the present invention.

[0030] Figure 2 Emission spectrum diagram of (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 1-x Eu x TiO3 (x = 0.06 - 0.08) prepared in Example 1 of the present invention under excitation at a wavelength of 465 nm.

[0031] Figure 3 Emission spectrum comparison diagram of (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 0.92 Eu 0.08 TiO3 prepared in Example 1 of the present invention and Sr 0.92 Eu 0.08 TiO3 prepared in Comparative Example 1 under excitation at a wavelength of 465 nm.

[0032] Figure 4 Emission spectrum comparison diagram of (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 0.92 Eu 0.08 TiO3 prepared in Example 1 of the present invention and Sr 0.92 Eu 0.08Fluorescence lifetime decay curve of TiO3 phosphor at 615 nm under excitation at 465 nm wavelength.

[0033] Figure 5 (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 0.92 Eu 0.08 Emission spectra of TiO3 prepared in Example 1 of the present invention at 25 °C to 150 °C.

[0034] Figure 6 Emission spectra of Sr 0.92 Eu 0.08 TiO3 prepared in Comparative Example 1 of the present invention at 25 °C to 150 °C.

[0035] Figure 7 (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 0.995 Sm 0.005 Emission spectra of TiO3 prepared in Example 2 of the present invention under excitation at 407 nm wavelength.

[0036] Figure 8 (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 0.995 Pr 0.005 Emission spectra of TiO3 prepared in Example 3 of the present invention under excitation at 362 nm wavelength.

[0037] Figure 9 (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 0.99 Er 0.01 Emission spectra of TiO3 prepared in Example 4 of the present invention under excitation at 369 nm wavelength.

[0038] Figure 10 Sr 0.98 Eu 0.02 (Zr 0.2 Ti 0.2 Sn 0.2 Ge 0.2 Se0.2 ) X-ray diffraction pattern of TiO3.

[0039] Figure 11 Sr prepared in Example 5 of the present invention 0.98 Eu 0.02 (Zr 0.2 Ti 0.2 Sn 0.2 Ge 0.2 Se 0.2 ) Emission spectrum of TiO3 obtained under excitation at a wavelength of 465 nm. Detailed implementation manners

[0040] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to specific examples. It should be understood that the specific examples described herein are only used to explain the present invention and do not limit the present invention.

[0041] In order to better illustrate the present invention, further examples will be given below through embodiments.

[0042] Example 1: (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 0.92 Eu 0.08 ) TiO3 ceramic phosphor, prepared by the sol-gel method.

[0043] The process steps are as follows: According to the equimolar ratio of each metal ion Ca 2+ , Ba 2+ , Sr 2+ , La 3+ , Na + , 3.680 mmol of calcium acetate, 3.680 mmol of barium acetate, 3.680 mmol of strontium acetate, 3.680 mmol of lanthanum nitrate, and 1.840 mmol of sodium carbonate are weighed respectively. According to 8 mol% Eu 3+Weigh 1.60 mmol of europium nitrate hexahydrate and add it to a beaker containing 30 mL of deionized water. Stir magnetically at room temperature, and then add 70 mL of acetic acid. Stir to dissolve it completely. Drop in 20.00 mmol of tetrabutyl titanate and stir at room temperature for 1 - 2 h to obtain a homogeneous sol. Preliminarily dry the prepared sol for 24 - 48 h. After the solvent has evaporated, place it in a drying oven and dry at 150 °C for 24 h. Put the dried powder in a porcelain boat, with a heating rate of 5 °C / min, heat it to 500 - 600 °C, hold for 3 h, then heat it to 800 - 1000 °C at a heating rate of 5 °C / min and hold for 2 h - 6 h. Finally, heat it to 1200 - 1400 °C at a heating rate of 5 °C / min and hold for 2 - 5 h. Then cool it in the furnace to obtain (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 0.92 Eu 0.08 TiO3 ceramic phosphor.

[0044] (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 1-x Eu x TiO3 (x = 0.06, 0.10) is prepared in exactly the same process steps as in Example 1, except for the content of europium nitrate hexahydrate, which is 1.20 mmol and 2.00 mmol, respectively, to obtain (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 0.94 Eu 0.06 TiO3, (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 0.90 Eu 0.10 TiO3.

[0045] Example 2: (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 0.995 Sm 0.005TiO3 ceramic phosphor is prepared by sol-gel method. The process steps are as follows: Weigh 3.980 mmol of calcium acetate, 3.980 mmol of barium acetate, 3.980 mmol of strontium acetate, 3.980 mmol of lanthanum nitrate, 1.990 mmol of sodium carbonate and 0.100 mmol of samarium nitrate hexahydrate in turn and add them into a beaker containing 30 mL of deionized water. Stir magnetically at room temperature. Then add 70 mL of acetic acid. After fully dissolving, drop 20.00 mmol of tetrabutyl titanate and stir at room temperature for 1 h to obtain a homogeneous sol. The prepared sol is preliminarily dried for 36 h. After the solvent evaporates, put it into a drying oven and dry it at 150 °C for 24 - 36 h. The obtained dried powder is mixed and ground in a mortar. The uniformly mixed powder is placed in a porcelain boat and heated in a muffle furnace at a heating rate of 5 °C / min to 500 - 600 °C, keep it warm for 2 h - 6 h, then heat it to 800 °C at a heating rate of 5 °C / min and keep it warm for 4 h. Finally, heat it to 1200 °C at a heating rate of 5 °C / min and keep it warm for 5 h. Then cool it with the furnace to obtain (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 0.995 Sm 0.005 TiO3 ceramic phosphor.

[0046] Example 3: (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 0.995 Pr 0.005 TiO3 ceramic phosphor is prepared by sol-gel method.

[0047] The process steps are as follows: Weigh 3.980 mmol of calcium acetate, 3.980 mmol of barium acetate, 3.980 mmol of strontium acetate, 3.980 mmol of lanthanum nitrate, 1.990 mmol of sodium carbonate, and 0.100 mmol of praseodymium nitrate hexahydrate, and add them successively to a beaker containing 30 mL of deionized water. Stir magnetically at room temperature. Then add 80 mL of acetic acid, and dropwise add 20.00 mmol of tetrabutyl titanate. Stir at room temperature for 1 h to obtain a homogeneous sol. Preliminarily dry the prepared sol for 36 - 48 h. After the solvent has evaporated, place it in a drying oven and dry at 150 °C for 36 - 48 h. Place the dried powder in a porcelain boat. Put the porcelain boat into a muffle furnace, with a heating rate of 5 °C / min, heat up to 500 - 600 °C, hold for 2 h - 6 h, then heat to 800 - 1000 °C at a heating rate of 10 °C / min, hold for 2 h - 6 h, and finally heat to 1200 - 1400 °C at a heating rate of 5 °C / min, hold for 2 h. Then cool with the furnace to obtain (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 0.995 Pr 0.005 TiO3 ceramic phosphor.

[0048] Example 4: (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 0.99 Er 0.01 TiO3 ceramic phosphor is prepared by the sol - gel method.

[0049] The process steps are as follows: Weigh 3.960 mmol of calcium acetate, 3.960 mmol of barium acetate, 3.960 mmol of strontium acetate, 3.960 mmol of lanthanum nitrate, 1.980 mmol of sodium carbonate, and 0.200 mmol of erbium nitrate hexahydrate. Add the weighed raw materials to a beaker containing 30 mL of deionized water. Stir magnetically at room temperature. Then add 70 mL of acetic acid, and dropwise add 20.00 mmol of tetrabutyl titanate. Stir at room temperature for 1 h to obtain a homogeneous sol. Preliminarily dry the prepared sol for 12 h. After the solvent has evaporated, place it in a drying oven and dry at 150 °C for 24 - 48 h. Place the obtained dried powder in a porcelain boat. Put the porcelain boat into a muffle furnace, with a heating rate of 5 °C / min, heat up to 500 - 600 °C, hold for 2 h - 6 h, then heat to 800 - 1000 °C at a heating rate of 10 °C / min, hold for 2 h - 6 h, and finally heat to 1200 - 1400 °C at a heating rate of 5 °C / min, hold for 2 - 5 h. Then cool with the furnace to obtain (Ca 0.2 Sr0.2 Ba 0.2 La 0.2 Na 0.2 ) 0.99 Er 0.01 ErTiO₃ ceramic phosphor.

[0050] Example 5: Sr 0.98 Eu 0.02 (Zr 0.2 Ti 0.2 Sn 0.2 Ge 0.2 Se 0.2 )O₃ ceramic phosphor, prepared by sol-gel method.

[0051] The process steps are as follows: Weigh 19.600 mmol of strontium acetate, 4 mmol of zirconium nitrate, 4 mmol of crystalline tin chloride, 4 mmol of germanium oxide, and 4 mmol of selenium oxide respectively, add them to a beaker containing 200 mL of deionized water, add 0.4 mmol of europium nitrate, and stir magnetically. In another beaker, drop 4 mmol of tetrabutyl titanate, add 4.08 mL of ethanol, 2.8 mL of acetic acid, and 2 g of polyvinylpyrrolidone. Stir magnetically at room temperature, then mix the solutions in the two beakers, stir at room temperature for 1 h to obtain a homogeneous sol. Preliminarily dry the prepared sol for 56 h, after the solvent evaporates, put it into an oven and dry at 150 °C for 48 h, and place the obtained dry powder in a porcelain boat. Put the porcelain boat into a muffle furnace, with a heating rate of 5 °C / min, heat up to 500 - 600 °C, keep warm for 2 - 6 h, then heat up to 800 - 1000 °C at a heating rate of 5 °C / min, keep warm for 2 - 6 h, and finally heat up to 1200 - 1400 °C at a heating rate of 5 °C / min, keep warm for 2 - 5 h. Then cool with the furnace to obtain Sr 0.98 Eu 0.02 (Zr 0.2 Ti 0.2 Sn 0.2 Ge 0.2 Se 0.2 )TiO₃ ceramic phosphor.

[0052] Comparative Example 1: Sr 0.92 Eu 0.08 TiO₃ ceramic phosphor, prepared by sol-gel method.

[0053] The process steps are as follows: Weigh 18.400 mmol of strontium acetate and 1.600 mmol of europium nitrate hexahydrate respectively, add them to a beaker containing 30 mL of deionized water, stir magnetically, then add 60 mL of acetic acid, and dropwise add 20.00 mmol of tetrabutyl titanate. Stir at room temperature for 1 h to obtain a homogeneous sol. The prepared sol is preliminarily dried for 12 h. After the solvent evaporates, place it in an oven and dry at 150 °C for 24 h. The obtained dried powder is placed in a porcelain boat. Put the porcelain boat into a muffle furnace, with a heating rate of 5 °C / min, heat up to 500 - 600 °C, hold for 2 - 6 h, then heat to 800 - 1000 °C at a heating rate of 10 °C / min and hold for 2 - 6 h. Finally, heat to 1200 - 1400 °C at a heating rate of 5 °C / min and hold for 2 - 5 h. Then cool with the furnace to obtain Sr 0.92 Eu 0.08 TiO3 ceramic phosphor.

[0054] Comparative example: Liu Wenfei, Preparation and Properties of Perovskite High-Entropy Oxide Powders and Ceramics, Chang'an University, 2023, pages 19 - 20

[0055] Dissolve 8 - 10 g of tetrabutyl titanate in 30 mL of absolute ethanol and 20 mL of glacial acetic acid to form a tetrabutyl titanate solution; weigh the corresponding mass of acetate according to the equimolar ratio of A-site in the system and dissolve it in 90 mL of deionized water and 10 mL of acetic acid to form an acetate solution. Subsequently, add the acetate solution to the tetrabutyl titanate solution, stir magnetically for 1 h, slowly add diluted ammonia water to the system, and after reaching the specified pH value and stabilizing, heat to 80 °C and stir until gelation occurs. Dry completely, grind, and sinter in an 80 °C oven. The sintering temperature curve is: heat at a rate of 5 °C / min to 400 °C, hold for 60 min, then heat to the sintering temperature at a heating rate of 10 °C / min, hold at the sintering temperature for 240 min, and finally cool with the furnace to room temperature to obtain perovskite high-entropy oxide powder.

[0056] According to the above literature, it is more conducive to obtaining a single-phase solid solution at a lower pH value (under acidic conditions). The present invention uses the sol-gel method to prepare A-site perovskite high-entropy oxide ceramics. The solution system used is a highly acidic solvent system (70 mL of acetic acid + 30 mL of deionized water). The La 3+ raw material is lanthanum nitrate, and lanthanum nitrate has better solubility in an acidic medium, which can effectively avoid the hydrolysis precipitation problem of La 3+ , and thus avoid the uneven distribution of A-site ions; in this acidic solution system, the hydrolysis rate of tetrabutyl titanate can be significantly inhibited. The present invention directly mixes all precursors under acidic conditions without separately preparing solutions and omits the pH adjustment step. During the process of adjusting the pH value, precipitation of metal ions with poor solubility may occur due to local over-alkalinity.

[0057] Attached Figure 1 X-ray diffraction pattern of (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 1-x Eu x TiO3 (x = 0.06 - 0.10) prepared in Example 1. It can be seen from the figure that with (Ca 0.2 Ba 0.2 Sr 0.2 La 0.2 Na 0.2 )TiO3 as the matrix, when the doping concentration x of Eu 3+ < 0.08, the phases of the synthesized ceramic powders are all in agreement with the standard card of SrTiO3 (PDF#84 - 0443), being a single phase, belonging to the cubic perovskite structure with the space group Pm - 3m. It shows that Eu 3+ has completely entered the SrTiO3 lattice to form a stable solid solution. Its four main diffraction peaks at 32.4°, 40.0°, 46.6°, and 57.9° respectively correspond to the (110), (111), (200), and (211) crystal planes of the SrTiO3 crystal, and the main diffraction peak is the (110) crystal plane; when the doping concentration x of Eu 3+ > 0.08, the diffraction peaks begin to split and the crystal structure is unstable. According to its phase, the optimal doping concentration of Eu 3+ is 0.08.

[0058] Attached Figure 2 Emission spectrum of (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 1-x Eu x TiO3 (x = 0.06 - 0.08) obtained under excitation at a wavelength of 465 nm. It can be seen from the figure that under 465 nm excitation, emission peaks of the sample appear at 580 nm, 592 nm, 615 nm, 653 nm, and 693 nm, corresponding to the 3+ of Eu 5 D0→ 7 F j(j＝0、1、2、3、4) transitions. Among them, the main emission peak is at 615 nm, and the corresponding 5 D0→ 7 F2 transition belongs to the electric dipole transition, indicating that Eu 3+ is in a position without inversion symmetry. With the increase of Eu 3+With the increase in doping concentration, the intensity of the emission peak also increases, which is due to Eu 3+ The increase in concentration leads to an increase in the number of luminescent centers, enhancing its emission intensity.

[0059] Attach Figure 3 (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 0.92 Eu 0.08 TiO3 prepared in Example 1 and the emission spectrum comparison diagram of Sr 0.92 Eu 0.08 TiO3 prepared in Comparative Example 1 under excitation at a wavelength of 465 nm. As can be seen from the figure, (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 0.92 Eu 0.08 TiO3 has a much higher emission intensity than Sr 0.92 Eu 0.08 TiO3, and its luminescence intensity is about 6 times that of Sr 0.92 Eu 0.08 TiO3.

[0060] Figure 4 (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 0.92 Eu 0.08 TiO3 prepared in Example 1 and the fluorescence lifetime decay curve at 615 nm of Sr 0.92 Eu 0.08 TiO3 prepared in Comparative Example 1 under excitation at a wavelength of 465 nm. Fitting was carried out using a double-exponential function, and it was calculated that the fluorescence lifetime of (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 0.92 Eu 0.08 TiO3 is 610.61 μs, and the fluorescence lifetime of Sr 0.92 Eu 0.08 TiO3 is 598.60 μs.

[0061] Attach Figures 5 - 6 Respectively, (Ca 0.2 Sr 0.2 Ba 0.2La 0.2 Na 0.2 ) 0.92 Eu 0.08 TiO3 and Sr prepared in Comparative Example 1 0.92 Eu 0.08 TiO3 emission spectra obtained at 25 °C to 300 °C. As the temperature increases, the phosphor always undergoes thermal quenching behavior, and high thermal stability is beneficial to maintaining high-intensity luminescence. As can be seen from the figure, Sr 0.92 Eu 0.08 TiO3 has already lost 40% of its luminescence intensity at 50 °C. At the same temperature, (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 0.92 Eu 0.08 TiO3 maintains a luminescence intensity of more than 90% at room temperature, and the thermal stability is significantly improved.

[0062] Attached Figures 7 - 9 are the (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 0.995 Sm 0.005 TiO3, (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 0.995 Pr 0.005 TiO3, (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 ) 0.99 Er 0.01 TiO3 emission spectra obtained under excitation at wavelengths of 407 nm, 362 nm, and 369 nm, respectively. As can be seen from the figure, they all exhibit the characteristic transitions of rare earth ions.

[0063] Attached Figure 10 is Sr prepared in Example 5 0.98 Eu 0.02 (Zr 0.2 Ti 0.2 Sn 0.2 Ge 0.2 Se 0.2) X-ray diffraction pattern of TiO3 phosphor. As can be seen from the figure, the phases of the synthesized ceramic powders are all in agreement with the standard card of SrSnO3 (PDF#74-1298), being a single phase and belonging to the cubic perovskite structure.

[0064] Appendix Figure 11 Sr prepared in Example 5 0.98 Eu 0.02 (Zr 0.2 Ti 0.2 Sn 0.2 Ge 0.2 Se 0.2 ) Emission spectrum of TiO3 obtained under excitation at a wavelength of 465 nm. As can be seen from the figure, the sample exhibits the characteristic emission peaks of Eu 3+ . Among them, the main emission peak is located at 615 nm, which also indicates that Eu 3+ is in a position without inversion symmetry.

Claims

1. A rare earth doped perovskite-type high entropy oxide fluorescent ceramic powder, characterized in that, Its chemical formula is A 1- x Ln x BO3, where the A-site is composed of Ca 2+ , Sr 2+ , Ba 2+ , La 3+ , Na + in an equimolar ratio of five cations, the B-site is composed of Ti 4+ , Zr 4+ , Sn 4 + , Ge 4+ , Hf 4+ , Se 4+ in an equimolar ratio of one or more of the following cations, Ln is Eu 3+ , Er 3+ , Sm 3+ , Pr 3+ , Tm 3+ , Dy 3 + One or more of them, and the doping concentration x ranges from 0 < x ≤ 0.

10.

2. The rare earth-doped perovskite-type high-entropy oxide fluorescent ceramic powder according to claim 1, wherein Its chemical formula is A 1-x Ln x BO3, where the A-site is composed of Ca 2+ , Sr 2+ , Ba 2+ , La 3+ , Na + and the five cations are composed in an equimolar ratio. The B-site is composed of Ti 4 + , Zr 4+ , Sn 4+ , Ge 4+ , Se 4+ and one or more of these cations are composed in an equimolar ratio.

3. The rare earth-doped perovskite-type high-entropy oxide fluorescent ceramic powder according to claim 1, wherein Its chemical formula is A 1-x Ln x BO3, where when the A site is Ca 2+ or Sr 2+ , and the B site is Ti 4+ , Zr 4+ , Sn 4+ , Ge 4+ , Se 4+ and the five cations are composed in an equimolar ratio.

4. The preparation method of the rare earth doped perovskite type high entropy oxide fluorescent ceramic powder as claimed in claims 1 to 2, characterized in that, It includes the following steps: Step (1): Weigh Ca and 2+ , Sr 2+ , Ba 2+ ,La 3+ 、Na + The raw material is added with Ln raw material and dissolved in the solvent, and Ti is added to the B position according to the molar ratio of the elements in the chemical formula. 4+ 、Zr 4+ Sn 4+ ,Ge 4+ 、Se 4+ One or more raw materials in equal molar ratios are added, and fully stirred and dissolved to obtain a sol; the solvent is any two or more of deionized water, acetic acid, anhydrous ethanol, and methanol; Step (2): Perform preliminary drying, dry gel, and grinding on the sol to obtain a powder; Step (3): Calcinate the powder at high temperature to obtain a rare earth ion-doped perovskite-type high-entropy oxide fluorescent ceramic powder.

5. The preparation method of the rare earth-doped perovskite-type high-entropy oxide fluorescent ceramic powder as claimed in claims 1 to 3, characterized in that, It includes the following steps: Step (1): When the A site is Ca 2+ or Sr 2+ , weigh one of the above-mentioned raw materials or two raw materials in equimolar ratio, and add the Ln raw material thereto and dissolve it in a solvent; weigh Ti 4+ , Zr 4+ , Sn 4+ , Ge 4+ , Se 4+ raw materials in equimolar ratio, add a stabilizer, and stir well to dissolve to obtain a sol; the solvent is any two or more of deionized water, acetic acid, absolute ethanol, and methanol. The stabilizer is polyethylene glycol or polyvinylpyrrolidone; Step (2): Perform preliminary drying, dry gel, and grinding on the sol to obtain a powder; Step (3): Calcinate the powder at high temperature to obtain a rare earth ion-doped perovskite-type high-entropy oxide fluorescent ceramic powder.

6. The preparation method of the rare earth-doped perovskite-type high-entropy oxide fluorescent ceramic powder as described in claims 4 and 5, characterized in that, In step (1), the raw material for the A-site element is a soluble metal salt, and one or more of soluble salts such as acetate, nitrate, carbonate, or hydrochloride can be selected. The color is white or light color to avoid the influence of black / dark color on the emission color.

7. The preparation method of the rare earth doped perovskite type high entropy oxide fluorescent ceramic powder as described in claims 4 and 5, characterized in that, In step (1), the raw material for the A-site element is a soluble metal salt, preferably acetate, nitrate, or carbonate.

8. The preparation method of the rare earth doped perovskite type high entropy oxide fluorescent ceramic powder as described in claims 4 and 5, characterized in that, In step (1), the raw material for the B-site element can be selected from soluble metal salts or metal oxides, and the color is white or light color; the raw material for the B-site element can be selected from one or more of soluble alcoholates, acetates, nitrates, carbonates, hydrochlorides, or metal oxides, etc.

9. The preparation method of the rare earth-doped perovskite-type high-entropy oxide fluorescent ceramic powder as described in claims 4 and 5, characterized in that, In step (2), the method for preliminary drying is to control the temperature at 25-50°C and volatilize the solvent for 12-48 h; the dry gel treatment method is to dry at 100-150°C for 12-72 h; in step (3), the heating rate for calcination is 5-10°C / min, heat up to 500-600°C, hold for 2 h-6 h, then heat to 800-1000°C at a heating rate of 5-10°C / min, hold for 2 h-6 h, and finally heat to 1200-1400°C at a heating rate of 2-6°C / min and hold for 2-5 h.

10. The application of the rare earth-doped perovskite-type high-entropy oxide fluorescent ceramic powder according to claims 1 to 3 in the field of luminescent materials such as lighting, transportation, military, decoration, biomedicine, and display imaging.

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