Temperature-stable relative permittivity from -70°C to 500°C in (Ba0.8 Ca0.2) TiO3- Bi (Mg0.5 Ti0.5) O3- NaNbO3 ceramics

Temperature-stable relaxor dielectrics have been developed in the solid solution system: 0.45Ba0.8Ca0.2TiO3-(0.55-x) Bi(Mg0.5Ti0.5)O3-xNaNbO3. Ceramics of composition x = 0 have a relative permittivity ?r = 950 ± 15% over a wide temperature range from +70°C to 600°C. Modification with NaNbO3 at x = 0.2 decreases the lower limiting temperature to -70°C, but also decreases relative permittivity such that ?r ∼ 600 ± 15% over the temperature range -70°C to 500°C. For composition x = 0.3, the low-temperature dispersion in loss tangent, tan δ, (at 1 kHz) shifts to lower temperature, giving tan δ values ≤0.02 across the temperature range -60°C to 300°C in combination with ?r ∼ 550 ± 15%. Values of dc resistivity for all samples are of the order of 1010 Ω m at 250°C and 107 Ω m at 400°C.