Dielectric Properties of Ba_(0.8)Ca_(0.2)TiO_3-Bi(Mg_(0.5),Ti_(0.5))O_3-NaNbO_3 Ceramics

摘要

Ceramics in the system 0.45Ba_(0.8)Ca_(0.2)TiO_3-(0.55-x)Bi (Mg_(0.5)Ti_(0.5))O_3-xNaNbO_3, x = 0-0.02 were fabricated by a conventional solid-state reaction route. X-ray powder diffraction indicated cubic or pseudocubic symmetry for all samples. The parent 0.45Ba_(0.8)Ca_(0.2)TiO_3-0.55Bi(Mg_(0.5)Ti_(0.5))O_3 composition is a relaxor dielectric with a near-stable temperature coefficient of relative permittivity, ε_r = 950 ± 10% across the temperature range 80℃-600℃. Incorporation of NaNbO_3 at x = 0.2 extends the lower working temperature to ≤25℃, with ε_r = 575% ± 15% from temperatures ≤25℃ to ＞400℃, and tan δ < 0.025 from 25℃ to 400℃. Values of dc resistivity ranged from ～10~9 Ω·m at 250℃ to ～10~6 Ω·m at 500℃. The properties suggest that this material may be of interest for high-temperature capacitor applications.