High-temperature dielectrics based on (1-x)(0.94Bi0.5Na0.5TiO3-0.06BaTiO3)-xNaNbO3 system

The microstructure, phase structure, ferroelectric and dielectric properties of (1-x)(0.94Bi0.5Na0.5TiO3-0.06BaTiO3)-xNaNbO3 (BNT-BT-xNN) ceramics were investigated as candidates for high-temperature capacitors with a working temperature far beyond 200 °C. The decreased polar rhombohedral phase shown in XRD and the weakened macroscopical polarization in P-E test indicate that NN addition can dilute the mutual coupling of polar nanoregions (PNRs), which is very conducive to flattening the curves of temperature dependent dielectric permittivity at the expense of a small reduction in dielectric permittivity values. Among all manufactured samples, those with composition of x = 0.10 showed a high permittivity of more than 2700 (1 kHz) and energy storage density of 0.61 J/cm3 (7 kV/mm) at 150 °C with a ΔC/C150°C varying no more than 15% in a wide temperature range of 54°C-318 °C. All of these exhibit wonderful temperature stable dielectric properties and indicated the promising future of BNT-BT-xNN system as high-temperature ceramic capacitors.