What is the different of combustion method and Sol-Gel method?

1.Combustion method

The combustion method is to add appropriate amount of water and combusting agents, such as urea, to the raw materials of phosphors. When the mixture of stoichiometric components is completely dissolved, it is heated in an electric furnace, and the mixture begins to burn when the burning point of the burning agent is reached in a day. Burning over. Reaction over. The combustion process of phosphor synthesized by combustion method can be divided into two forms: self propagating and flaming. Self-Propagation is when the reactant starts at one end and gradually travels automatically to the other until the reaction terminates. An explosion is the immediate occurrence of the entire reaction, releasing a large amount of heat, and the reaction is as intense as an explosion. The synthesis of phosphors by combustion method can reduce the heating temperature of the electric furnace and reduce the energy consumption. On the other hand, the gases produced by the combustion process can protect the easily oxidized ions. Therefore, it is not necessary to use the other reductive protective atmosphere during the reaction, thus reducing the cost. The shortcoming of combustion method is that there may be heterogenous phase in the process of preparing phosphors, so the final product purity is not high, which leads to the degradation of phosphor luminescence performance.

2.Sol-Gel method

The preparation of phosphors by sol-gel is a promising method for the synthesis of phosphors by soft chemistry. Sols refer to very small solid particles below 100 nm) suspended indefinitely in liquid phase depending on Brownian motion. "Gel" refers to a solid with a spatial network of colloidal particles or polymer molecules formed by cross-linking with each other to accommodate liquid components.

Structured liquids and solids are highly dispersed systems. According to the different materials used, sol-gel can be divided into two categories:

one is sol-gel in aqueous solution and the other is sol-gel in alcohol salt.

The basic process and principle of sol-gel process is that inorganic salts, metal alcohols, and other organic salts are dissolved in inorganic solvents (usually water) or organic solvents, and then a homogeneous solution is obtained. In the hydrolysis, alcoholysis, chelation between solute and solvent, the reaction product aggregates into nanoparticles and then forms a sol. After drying and evaporating, the sol will be converted into gel. After drying and roasting, the needed phosphors can be obtained.

Compared with the traditional high temperature solid state method, the sol-gel method can synthesize phosphors with smaller particle size and nanometer level, and the phosphors prepared by sol-gel method have higher purity. The composition of phosphors is uniform, the synthesis temperature is low, and the particle size can be controlled. However, the sol-gel method also has the following defects: the process of preparing phosphors is relatively complex and it takes a certain time to produce gels, so the preparation period is long and it is difficult to achieve industrial production. This results in a non-radiative transition, which results in the low efficiency luminescence of the phosphor.

This article is from Allicdata Electronics.