Performances variations of BiFeO3-based ceramics induced by additives with diverse phase structures

Abstract

Herein, four perovskites with different space groups, namely PbTiO₃ (P4mm, T phase), SrTiO₃ (Pmm, C phase), CaTiO₃ (Pbnm, O phase) and MgTiO₃ (R, R phase), were added to BiFeO₃–BaTiO₃ ceramic, aiming at affecting both the structures and properties. Both the R and T phases coexisted in the phase structures of (1 − x)(0.725BiFeO₃–0.275BaTiO₃)–xABO₃ + 0.8 mol% MnO₂ (abbreviated as BFBT, BFBT-xPT, BFBT-xST, BFBT-xCT and BFBT-xMT) ceramics. Apparently, the displacement of B atoms was presented in BFBT-6PT, BFBT-6ST and BFBT-6CT, resulting in higher polarity than the BFBT sample. Moreover, the electronic structures calculated by first principles theory based on DFT were in line with the experimental results of P–E loops. The characteristic of the ferroelectric state was observed in the BFBT and BFBT-6PT samples, and the relaxation ferroelectric behaviour was detected in the BFBT-6ST, BFBT-6CT and BFBT-6MT samples by the slim P–E loops, broad Curie peaks, red shift of Raman peaks, flat I–V curves, as well as the PFM measurement. The BFBT-6PT ceramics showed a plump grain size (5.39 μm), heightened T_c (526 °C), improved P_r (23.4852 μC cm⁻²) and enhanced d₃₃ values (171 pC N⁻¹). The addition of CaTiO₃ and SrTiO₃ mildly decreased the grain size of BF-BT. MgTiO₃ reduced the dielectric and piezoelectric performances as well as the grain size sharply. This study provided a supplement for the study of BF-BT ceramics.