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High temperature solid state reaction

Last Update Time: 2018-10-12 10:59:20
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High temperature solid state reaction

Solid-state reaction is a physical and chemical phenomenon in the preparation of phosphors at high temperature.The traditional method of phosphor synthesis is realized by solid state reaction at high temperature.The reaction of each component in this method is determined by three factors,namely,the reactivity of the solid component itself,the crystal structure of the raw material and the defects in the lattice of the material.The more defects in the crystal lattice of phosphor,the higher the mass transfer ability of each other in the high temperature solid state reaction,and the higher the reaction rate is,the more thorough the reaction process is.More importantly,the high temperature solid state reaction takes place at the particle interface of all raw materials,which requires the fullest possible contact between the reactants.Moreover,the smaller the reactant particles,the larger the specific surface area of the reactants,and the larger the composition of each group.

The contact area of the reactants will be increased, which is beneficial to the promotion of the reaction rate and the good development of the reaction at high temperature. Therefore,the full grinding of phosphor raw materials is a very important prerequisite for the preparation of phosphors.In addition, external factors,such as sintering temperature,pressure and flux,affect the effect of high temperature solid state reaction.The steps of the high temperature solid state reaction are shown in Fig.One of the most important factors determining the solid state reaction of phosphors is the new nucleation and diffusion rate in the synthesis process.The phosphors prepared by high temperature solid state process generally need some follow-up treatment technology,such as crushing,powder sorting, cleaning and filtering.

The advantages of high temperature solid state reaction are that the process is simple and the industrial production is easy to be realized.

The crystal quality of the obtained phosphors is better and the surface defects of the phosphors are less.Its disadvantages are:

When the sintering temperature is high and the sintering time is as long as the sintering time,the resulting phosphors are easy to be agglomerated.

The luminescent properties of phosphors will be decreased after ball milling.