Effect of Sintering Aids on Microstructures and PTCR Characteristics of (Sr _0.2 Ba _0.8 )TiO ₃ Ceramics

Abstract

The effects of liquid‐phase sintering aids on the microstructures and PTCR characteristics of (Sr 0.2 Ba 0.8 )TiO 3 materials have been studied. The grain size of sintered materials monotonically decreases with increasing content of Al 2 O 3 –SiO 2 –TiO 2 (AST). The ultimate PTCR properties with ρ ht /ρ rt as great as 10 5.61 are obtained for fine‐grain (10‐μm) samples, which contain 12.5 mol% AST and were sintered at 1350°C for 1.5 h. The quantity of liquid phase formed due to eutectic reaction between AST and (Sr,Ba)TiO 3 is presumably the prime factor in determining the grain size of samples. The grains grow rapidly at the sintering temperature in the first stage until the liquid phase residing at the grain boundaries reaches certain critical thickness such that the liquid–solid interfacial energy dominates the mechanism of grain growth.