The orientational growth of grains in doped BaTiO3 PTCR materials by microwave sintering

Doped BaTiO3 (BTO) PTCR materials were sintered by microwave (MW) of 2.45 GHz at 1250 °C for 15 min. For comparison, identical samples (Ø30 mm×45 mm) were also sintered by conventional (CO) SiMo furnace at 1350 °C for 2 h. The experimental results show that the MW-sintered samples have a much greater axial linear shrinkage rate of 48% vs. the rate for the CO-sintered sample of 26%. This result has not yet been reported in other researcher works. Marked differences were also observed in the microstructure of the two samples by SEM, the grains in the CO-sintered sample showing on ecliptic spherical shape, whereas in MW-sintered samples the grains show an orientational strip-like microstructure. The XRD analysis indicates that the perovskite structure of MW-sintered BTO is tetragonal, whereas the CO-sintered sample is cubic.