Preparation of Ultrafine Ceramic Powder Used for Making PTCR Ceramics by Sol-gel Method

Amorphous gel powder containing Ba, Sr, Ca, Ti, Si, Mn, Li and Y elements has been prepared by a modified sol-gel method, the ultrafine PTCR (Positive Temperature Coefficient of Resistance) powder was obtained through calcination for 2 h at 800℃ in air. According to XRD, DSC, BET and SEM. it can be concluded that it's crystal structure is cubical perovskite phase at room temperature, it's average crystallite size is about 28.4nm (using the Debye-Scherrer formula) or about 40 nm (using BET) or about 50nm(using SEM), it's specific surface area is 24.80 m²/g, and which is two twice as much as that of the sample prepared by old sol-gel method^[l,2], it's particle size displays normal distribution with average particle size of 437.2nm.