Origin of ultrahigh thermal stability on dielectric permittivity and dipole glass-like behavior of 0.4Ba0.8Ca0.2TiO3-0.6Bi(Mg0.5Ti0.5)O3 based ceramics

Abstract

The 0.4Ba0.8Ca0.2TiO3-0.6Bi(Mg0.5Ti0.5)O3 (BCT-BMT) and 5 mol% Si doped 0.4Ba0.8Ca0.2TiO3-0.6Bi(Mg0.5Ti0.5)O3 (BCST-BMT) ceramics with a pseudo-cubic crystal structure were prepared. Both as-prepared and O2 annealing ceramics (BCT-BMT-O2 and BCST-BMT-O2) exhibit a typical re-entrant dipole-glass-like relaxor behavior and excellent thermal stability of dielectric permittivity above Tm. A statistical model was employed to describe the temperature dependence of dielectric permittivity, which reveals the origin of the special dielectric properties. The large dielectric permittivity is attributed to the weakly interacting polar nanoregions (PNRs) associated with complex ionic substitution of both the A-site and B-site. The ultrahigh thermal stability is related to the thermal distribution of active dipoles. The Si doped BCT-BMT ceramic shows that the capacitance variation are lower than ± 5 % (1209 ± 60) in a wide temperature range from 437 K to 796 K with a low dielectric loss (tanδ < 0.025) from 443 K to 714 K, indicating a promising material for use in high-temperature capacitors.