High-temperature dielectrics based on 0.95(0.94Bi _0.5 Na _0.5 TiO ₃ -0.07BiAlO ₃ )-0.05K _0.5 Na _0.5 NbO ₃

The high temperature capacitors operated in some harsh conditions require dielectric ceramics with stable permittivity, low dielectric loss and high resistivity to temperatures above 200 °C. In this work, high temperature dielectrics based on (1-x-y)Bi _0.5 Na _0.5 TiO ₃ -xBiAlO ₃ -yK _0.5 Na _0.5 NbO ₃ ceramics were designed and prepared. The introduction of BiAlO ₃ leads to the reduction of dielectric loss due to the formation of defect dipoles. And the introduction of K _0.5 Na _0.5 NbO ₃ leads to the disruption of long-range ferroelectric order, which is helpful to increase the temperature stability of permittivity. The composition of x = 0.07 and y = 0.05 has a stable permittivity between 86.5 °C and 324.5 °C and dielectric loss below 0.02 in the temperature range of 110 °C–336 °C. Therefore, this system will be one of promising candidates of dielectrics used for high-temperature capacitors.