High-temperature dielectrics in CaZrO_3-modified Bi_(1/2)Na_(1/2)TiO_3-based lead-free ceramics

摘要

Materials in two composition regimes, Bi_(1/2)Na_(1/2)TiO_3-BaTiO_3-CaZrO_3 (BNT-BT-CZ) and Bi_(1/2)Na_(1/2)TiO_3-BaTiO_3-K_(0.5)Na_(0.5)NbO_3-CaZrO_3 (BNT-BT-KNN-CZ), were synthesized via the mixed oxide route and their structural, dielectric and electrical properties were investigated. CZ was identified to render the two local maxima in permittivity more diffused. This resulted in temperature-insensitive relative permittivity spectra with average values from ~470 up to ~2300 and operational windows of at least ~400 °C with less than 15% of variation in the temperature range from -100 up to above 500 °C. Moreover, loss factors are below ~10% and RC constants range from ~0.03 s up to ~4 s at 300 deg C. The materials of current investigation are highly attractive for developing capacitors of wide temperature usage.