Relaxor ferroelectric behaviour observed in (Ca0.5Sr0.5Ba0.5Pb0.5)Nb2O7 perovskite layered structure ceramics

Relaxor ferroelectric behaviour was observed in perovskite layered structure (PLS) (Ca_0.5Sr_0.5Ba_0.5Pb_0.5)Nb₂O₇ (CSBPN) ceramics engineered using the high entropy approach. The CSBPN ceramics were sintered at 1350 °C and are single-phase with an orthorhombic structure (Cmcm space group) at room temperature. Their relaxor ferroelectric behaviour is characterized by a broad and frequency-dependent permittivity maximum and a current peak around zero electric field in the hysteresis loop. The presence of polar nanoregions is supported by piezoresponse force microscopy images. The value of the relative permittivity ?′ = 130 at 1 kHz and room temperature is much larger than that for conventional PLS ceramics Sr₂Nb₂O₇ (?′ = 42) and Ca₂Nb₂O₇ (?′ = 38). This can be attributed to the presence of polar nanoregions and the lattice distortion effect in high entropy materials. The appealing dielectric and relaxor behaviour of CSBPN ceramics confirms the efficacy of the high entropy approach to obtain improved properties.