Phase structure, microstructure and dielectric properties of (K_0.5Na_0.5)NbO₃-LaFeO₃ high-temperature dielectric ceramics

The (1-x)(K_0.5Na_0.5)NbO₃-xLaFeO₃ (abbreviated as (1-x)KNN-xLF, x = 0-0.03) ceramics were synthesized by the conventional solid-state sintering method. X-ray diffraction analysis shows that the phase structure of the (1-x)KNN-xLF ceramics transfers from orthorhombic to pseudocubic with increasing the LF content. The SEM studies reveal that a small amount of LF, as a grain growth inhibitor, has an evident effect on grain size reduction. The (1-x)KNN-xLF (x = 0.02) ceramics show high permittivity maximum (near 2000) and low dielectric loss (<5%) in the temperature range of 100-400°C, and the capacitance variation (ΔC/C_150°C) is keeping within ±15%, indicating the potential application for the high-temperature capacitors.