Phase Structure, Microstructure and Dielectric Properties of (K _0.5 Na _0.5 )NbO ₃ ‐LaFeO ₃ High‐Temperature Dielectric Ceramics

The (1‐ x )(K _0.5 Na _0.5 )NbO ₃ ‐ x LaFeO ₃ (abbreviated as (1‐ x )KNN‐ x LF , 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‐ x LF 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‐ x LF ( 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.