BaTiO_3-Bi(Zn_(1/2)Ti_(1/2))O_3-BiScO_3 Ceramics for High-Temperature Capacitor Applications

摘要

Ceramics based on solid solutions of xBaTiO_3-(100-x)(0.5Bi (Zn_(1/2)Ti_(1/2))O_3-0.5BiScO_3), where x = 50, 55, and 60 were prepared by solid-state reaction which resulted in a single perovskite phase with pseudocubic symmetry. Dielectric property measurements revealed a high relative permittivity (>1000), which could be modified with the addition of Bi(Zn_(1/2) Ti_(1/2))O_3 (BZT) and BiScO_3 (BS) to engineer a temperature-stable dielectric response with a temperature coefficient of permittivity (TCε) as low as -182 ppm/℃. By incorporating 2 mol% Ba vacancies into the stoichiometry, the resistivity increased significantly, especially at high temperatures (>200℃). Vogel-Fulcher analysis of the permittivity data showed that the materials exhibited freezing of polar nanoregions over the range of 100-150 K. An analysis of optical absorption near the band edge for the Ba-deficient compositions suggested that the enhanced resistivity values were linked to a decrease in the concentration of defect states. An activation energy of ～1.4 eV was obtained from DC resistivity measurements suggesting that an intrinsic conduction mechanism played a major role in the high temperature conductivity. Finally, multilayer capacitors based on these compositions were fabricated, which exhibited dielectric properties comparable to the bulk material. Based on these results, this family of materials has great promise for high-temperature capacitor applications.