Temperature‐Stable Relative Permittivity from −70°C to 500°C in ( Ba 0.8 Ca 0.2 ) TiO 3 – Bi ( Mg 0.5 Ti 0.5 ) O 3 – NaNbO 3 Ceramics

Temperature‐stable relaxor dielectrics have been developed in the solid solution system: 0.45 Ba 0.8 Ca 0.2 TiO 3 –(0.55 −  x ) Bi ( Mg 0.5 Ti 0.5 ) O 3 – x NaNbO 3 . Ceramics of composition x  = 0 have a relative permittivity ɛ r  = 950 ± 15% over a wide temperature range from +70°C to 600°C. Modification with NaNbO 3 at x  = 0.2 decreases the lower limiting temperature to −70°C, but also decreases relative permittivity such that ɛ 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 ɛ r  ~ 550 ± 15%. Values of dc resistivity for all samples are of the order of 10 10  Ω m at 250°C and 10 7  Ω m at 400°C.