Impact of two-step calcination on microstructure, phase, electronic, and dielectric properties of KCa₂Nb₃O₁₀ bulk layered perovskite

The effects of varying calcination temperature, K content, and the number of calcination steps in the dielectric performance of KCa₂Nb₃O₁₀ synthesized via solid-state reaction are investigated. Adding an extra calcination step at 500°C followed by another calcination at 1100°C suppressed the formation of secondary phases while maximizing the relative density (95%) and the average grain area (2.12 μm²). The first calcination at 500°C ensures the formation of intermediate phases (KNbO₃ and Ca₂Nb₂O₇), which are prerequisites for single-phase KCa₂Nb₃O₁₀ synthesis. A significantly high dielectric constant of 352 at 100k Hz is achieved in the two-step calcined sample despite the low sintering temperature of 1250°C. The highest resistivity of the two-step calcined sample (2 × 10⁸ Ω cm) obtained from complex impedance analysis supports its lowest dielectric loss (0.034 at 100k Hz). When the two-step calcined KCa₂Nb₃O₁₀ powder is exfoliated, much higher dielectric properties of Ca₂Nb₃O₁₀ nanosheets are expected.