Effect of Firing Atmosphere on Densification of Semiconducting (Ba, Sr)TiO 3 Ceramics and Their Dielectric Properties and Varistor Characteristics

A new atmospheric-gas firing process is demonstrated to be effective for the densification of semiconducting (Ba, Sr)TiO 3 ceramics having a positive temperature coefficient of resistivity (PTCR). In the new atmospheric-gas firing process, oxygen atmosphere is introduced in the heating stage of the former reduction-reoxidation firing. Thereby the density of ceramics was increased to 97% from 91%. The optimum Mn concentration for a capacitive varistor increased to 0.20 atm% from 0.11 atm% compared to previous samples with porous ceramic bodies.