Abstract
Effect of post-sintering treatment on PTCR behavior of (Sr 0.2 Ba 0.8 )TiO 3 materials prepared by microwave-sintering (ms) process was compared to that prepared by rapid thermal sintering (RTS) process. The microwave-sintering process needed only 1130°C-40 min to effectively densify (Sr 0.2 Ba 0.8 )TiO 3 materials. The grain size was around 6 μm and PTCR characteristics was around ρ max ,/ρ min ≈ 10 1.75 , with T c = 50°C. Lowering the cooling rate after sintering substantially increases the resistivity jump (ρ max /ρ min ) from 10 2 to 10 3.4 , without altering the microstructure. The annealing at 1250°C for 2 h markedly increased the resistivity jump to (ρ max /ρ min )≈10 6 . On the other hand, the rapid thermal sintering (RTS) process required 1320°C-30 min to fully develop the good microstructure (∼15μm) and PTCR property (ρ max /ρ min ∼ 10 3.0 ). Post-sintering process, including cooling rate control and annealing, did not improve the electrical properties of these samples, that is ascribed to the slow-cooling rate characteristics of RTS-process for a temperature lower than 800°C.