(K0.5Bi0.5)ZrO3 (KBZ) lead-free perovskite compound: Structural study and physical properties

Abstract

The structural study of (K0.5Bi0.5)ZrO3 compound (KBZ) evidenced a cubic ABO3 perovskite structure (space group: No 221 Pm3‾m, lattice parameter: a = 0.4157 nm). Above room temperature, the lattice parameter increases linearly, with linear expansion coefficient α = 6.4 × 10−6 K−1. No phase transition or decomposition occurs up to 1273 K (1000 °C). Below room temperature, small anomalies in Differential Scanning Calorimetry (DSC) and dielectric losses (tan(δ)) remain structurally unexplained and will need further investigation. Furthermore, KBZ appears as difficult to sinter. Although the A-site of the ABO3 perovskite lattice is occupied by two ions of different valences (K+/Bi3+, mixed occupancy), we did not detect relaxor behaviour in KBZ dielectric properties. However, electrostriction was observed at room temperature. This property, combined to the limited thermal evolution of the relative permittivity indicate that KBZ may be an interesting material, provided that the sintering can be improved.