How to prepare long afterglow luminescent materials(1)

1 high-temperature solid-phase method

The use of high-temperature solid-phase reaction method for the preparation of long afterglow materials is a more traditional method, this method is more widely used. In general, the general operation of the solid-phase reaction is to solid powder as raw materials. Will meet the requirements of purity of raw materials in a certain proportion of weighing, and add a certain amount of flux fully mixed and ground, and then under certain conditions (temperature, atmosphere, time, etc.) for sintering. 

According to the precise formula of the stoichiometric ratio of light-emitting materials, placed in a high-temperature resistance furnace within a certain protective gas atmosphere or reducing atmosphere 900 ℃ ~ 1450 ℃ scorching 2h-5h that is. Burning process, co-solvent and dopant ion types and ratios, etc. have a significant impact on the structure and luminous properties of long afterglow luminescent materials.

As the high-temperature solid-phase method of reaction conditions control, reducing agent use, flux selection and raw material formulation are increasingly optimized, the production process is mature, and therefore is widely used. For example, the red long afterglow material of sulfide system is obtained by mixing and roasting alkaline earth metal carbonate, sulfur powder, and selecting suitable rare earth oxides and fluxes, and also directly using alkaline earth metal sulfate and rare earth oxides, fluxes mixed roasting process. 

2 Sol-gel method

For high-temperature solid-phase method of burning temperature, the preparation of sub-light-emitting material particles are coarse, the crystalline shape of the material after ball milling is vulnerable to destruction of the shortcomings, people have developed many other methods. Among them, the sol-gel method as a wet chemical method in the materials science community has attracted widespread attention. This method first originated in the 18th century, and the application of this method has been very extensive.

Sol-gel method is a method that uses a specific material precursor to form a sol under certain conditions of hydrolysis, and then by solvent volatilization and heating treatment, the sol is transformed into a gel with a network-like structure, and then into an appropriate post-treatment process to form nanomaterials.

Raw material-->dispersible system-->sol-->gel-->nanomaterial

The preparation of luminescent materials using sol-gel technology is mainly by using metal alcohol salts, i.e., metal alcohol salts are used as raw materials for hydrolysis reaction and polymerization reaction to obtain sols and gels.Zhang Dong and his co-workers prepared ZnAl2O4:Mn materials using sol-gel method with sintering temperature 100 to 200°C lower than the conventional method. 

In recent years, the method of inorganic salt complexes for the preparation of sol-gels has gradually received attention, which is mainly prepared by the Pechin method, which uses citric acid to prepare sol-gels by esterification reaction with ethylene glycol, this method is experimentally fast and simple, and the cost is lower than the metal alcohol salt method.