Improvement of the Electrical Properties in Ba(Ti_(0.92)Sn_(0.08))O_3 Lead-Free Ceramics by Ca Addition and Sintering Profile

摘要

(Ba_(1-x)Ca_x)(Ti_(0.92)Sn_(0.08))O_3 lead-free ceramics were prepared using two different sintering methods: a conventional sintering (CS) and a two-step sintering (TSS) techniques. It was considered the different sintering temperatures and profiles can be used to optimize the density, microstructure and electrical properties. The effects of Ca content on phase formation, densification, microstructure, and electrical properties were investigated. Tetragonal structure perovskite was obtained in all samples. Hence, Ca content and sintering profile did not affect the crystal structure. Compositional analysis is ascribed to the occupancy of some Ca~(2+) to the Ti~(4+)sites. The x = 0 sample sintered by a two-step sintering achieved the highest density of 5.73 ± 0.01 g/cm~3 (95% theoretical density). The grain size decreased when the Ca content and sintering temperature increased. Scanning electron micrographs showed that the two-step sintering produced a smaller grain size than those of the conventional ones, resulted from lower the holding temperature. It also got that the two-step sintering and Ca addition improved electrical properties of samples. At 1 kHz, the x = 0.04 exhibited the highest room-temperature dielectric constant reaching to 4,250 with a relatively low dielectric loss. The increasing of Ca content and the holding temperature affected the increasing of Curie temperature. AC complex impedance spectroscopy technique was also used to acquire the electrical properties of (Ba_(1-x)Ca_x)(Ti_(0.92)Sn_(0.08))O_3 ceramics. Sample with x = 0.04 sintered by conventional sintering achieved the best piezoelectric charge constant (d_(33)) of 262.0 pC/N. The (Ba_(0.96)Ca_(0.04))(Ti_(0.92)Sn_(0.08))O_3 lead-free ceramic has a potential application in piezoelectric energy harvester and can be applied in modern low-power electronic products.