1. Ingredients
At present, the vast majority of domestic and foreign manufacturers use the solid-phase synthesis process. The raw materials used are BaCO3, SrCO3, Pb3O4, TiO2, Nb2O5, MnCO3, SiO2 and other powders, and the purity should generally be above 99.5%. The purity of the raw materials, the variety and content of impurities contained, the chemical activity of the raw materials, etc., all have a great impact on the performance of the PTC final product. The accuracy of ingredients also has a great impact on product performance.
2. Ball mill to destroy and remove water
Put several kinds of raw material powders, grinding balls and pure water weighed into the ball mill for ball milling and destruction, and mix them evenly. The ball-milled raw materials can be simply put into an oven for drying, or can be dried by using techniques such as filtration, centrifugation, and vacuum filtration to remove water.
3. Solid Phase Synthesis
Solid-phase synthesis is also called pre-sintering. The mixed raw materials are put into a high-temperature furnace for reaction to form a uniform solid solution. The general formula of the solid solution can be written as (Bax, Sry, Pbz) TiO3, where x+y+z=1 , The temperature of solid-phase synthesis is selected between 1000 and 1250 ℃ according to the material and the ratio, and the holding time is 2 to 4 hours.
4. Secondary ball milling
After solid-phase synthesis, the material is agglomerated, and there is a certain grain growth, which needs to be destroyed by ball milling to facilitate sintering. The technique of secondary ball milling is similar to that of pre-synthesis ball milling.
5. Forming
PTC materials can be made into various styles, such as: wafers, squares, honeycombs, etc. The sheet-like element is formed by dry pressing, adding a suitable PVA solution to the material, and then granulating the material by sieving or spray drying, and then pressing and forming on a punching machine. The honeycomb elements are formed using extrusion techniques.
6. Firing
The formed green sheet is put into a high-temperature furnace, and the semiconductor ceramics with the required PTC characteristics are fired according to certain firing preconditions. The firing curve and firing air have a great influence on the performance of the product, and must be strictly controlled in production in order to improve product performance and yield.
Click To Know More
