Significant impact of TiO2 purity on the phase structure and electrical properties of BiFeO3–BaTiO3 lead-free piezoelectric ceramics

In many studies, the properties of BiFeO 3 –BaTiO 3 (BF–BT) ceramics vary greatly using different raw reagents, which makes it challenging to obtain reliable and repeatable properties of BF–BT-based devices. In this work, 0.7BiFeO 3 –0.3BaTiO 3 (0.7BF–0.3BT) ceramics were fabricated by a conventional solid-phase synthesis using TiO 2 reagents with varied purities of 98%, 99%, 99.9%, and 99.99%, respectively. The phase structure, microstructure, ferroelectric, and piezoelectric properties were comprehensively studied. All compositions of the ceramics exhibit a pseudo-cubic phase perovskite structure, and the fraction of the rhombohedral phase increases with increasing the TiO 2 purity. Additionally, backscattered electron images and energy-dispersive spectroscopy revealed an obvious core–shell structure within grains. In particular, the 0.7BF–0.3BT ceramics prepared with 98% purity TiO 2 exhibited superior ferroelectric and piezoelectric properties, d 33 ∼ 220 pC/N and d 33 ∗ $d_{{\mathrm{33}}}^{\;*}$ ∼ 230 pm/V. The ceramics prepared with higher purity TiO 2 suffered from severe leakage conduction, which can be well addressed by adding excess TiO 2 . Our work reveals the importance of different grades of purity TiO 2 on the electrical properties of BF–BT ceramics.