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

ABSTRACT 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.