Preparation of inorganic fluorescent materials

Yu Lanping [80] summarized the preparation methods of inorganic fluorescent materials into the following eight kinds.
(1) High-temperature solid-state method-High-temperature solid-state method is a traditional preparation method of inorganic fluorescent materials. Uniformly mixing the luminescent matrix and the activator according to a certain proportion, burning at 1000-1500℃ for several hours in a reducing atmosphere, cooling and pulverizing to obtain the finished product. For example, Zns :Cu=9911 is mixed, burned at 1300℃ for 10h, cooled and crushed to obtain fluorescent pigment for powder coating. Adopt reagent (NH); HPO4、Ce(NOR )s·6H; 0, Tb, O7, La2Os, Lie CO3 and AI(OH)3 can be sintered in a high temperature furnace at 1180~1260℃ to prepare green phosphate phosphors.
(2) Sol-gel method Sol-gel method is a new preparation method in recent years. According to the different reaction media, it can be divided into aqueous solution sol-gel method and alkoxide solution sol-gel method. Generally, the accurately weighed reaction mixture is dissolved with nitric acid, then added with alkoxide, and refluxed in a constant temperature water bath for several hours until a uniform and transparent gel is formed. The gel is dried, crushed and burned to obtain the product.
(3) Surface diffusion method-The surface diffusion method adopts the step-by-step synthesis process of solid matrix and activator, so that the activator adheres to the surface of the prefabricated matrix and carries out reduction diffusion reaction. Liu Yingliang and others [3] took the lead in proposing the “surface diffusion method”. In the preparation process of the blue component BaMgAloO7∶Eu of rare earth tricolor luminescent materials, firstly, the phosphor matrix BaMgAlyoO was synthesized by high-temperature solid-state method. After the matrix powder reacted with a certain concentration of EuClk urea solution in water bath for a period of time, Eu(OH)a was precipitated on the surface of the matrix particles, cooled, filtered and dried, and carbon powder was used at 1200℃.
(4) Homogeneous precipitation method, which generally uses small molecular substances as precipitants, such as urea, oxalic acid, etc., uses ammonia water to adjust the pH value, adjusts the growth size of crystal particles by controlling the homogeneous reaction time, and obtains the product after separation, washing and drying. Homogeneous precipitation method is the main synthesis method of nano-fluorescent materials.
(5) The self-propagating combustion method, such as Kinsley, uses metal nitrate of fluorescent matrix as oxidant and glycine or carbonic acid trap as fuel, which are evenly mixed to obtain precursor solution. When heated and concentrated, the solution undergoes a violent combustion reaction to obtain a loose foamed solid. The preparation conditions, such as the ratio of precursors and annealing temperature, have great influence on the brightness, particle structure and morphology of fluorescent materials.
(6) Thermal decomposition method: Thermal decomposition method is the main method to synthesize compound fluoride. The method comprises the following steps: heating and refluxing the reactants prepared according to the stoichiometric ratio in an aqueous solution, and concentrating the volatile solvent to prepare a complex precursor. The precursor is burned at high temperature to decompose the complex. Different thermal decomposition temperatures affect the particle size and crystal form of the product. For CDs; For Og ∶Eu, it is easier to prepare pure cubic products without monoclinic phase by thermal decomposition method than by self-propagating combustion method, and the luminous intensity is high.
(7) Microwave synthesis method, using ultra-high frequency oscillation of microwave, can produce huge thermal effect in a short time. Various phosphors such as oxide, sulfide, phosphate and silicate have been successfully synthesized by microwave synthesis. It is prepared by uniformly mixing reactants in a certain proportion, heating in microwave for a period of time, taking out and cooling. The advantages of microwave synthesis are: ① less solvent consumption, avoiding fluorescence quenching caused by solvent molecules; ② short reaction time, high product yield; ③ adjusting product structure, improving fluorescence performance; ④ high efficiency and energy saving.
(8) Vapor deposition method, which is a new technology for preparing inorganic nanomaterials. It uses reactant gas with high pressure at medium temperature to deposit high melting point phase. B, M, Tissues, etc. used the method of CO laser heating vapor deposition to prepare nanoparticles with a particle size of 4~18nm. By adjusting the parameters of the deposition process, the chemical composition, morphology and crystal configuration of the deposited substances are controlled.
With the development and progress of preparation technology of inorganic fluorescent materials, its application fields are constantly expanding. In recent years, the preparation and application of nano-fluorescent materials have become a new hot spot in the research of fluorescent materials. At the same time, electroluminescent, electroluminescent and scintillation fluorescent materials also need to be developed.