High Curie temperature BiFeO3-BaTiO3 lead-free piezoelectric ceramics: Ga3+ doping and enhanced insulation properties

BiFeO 3 -BaTiO 3 is a promising high-temperature lead-free piezo-ceramics due to its high Curie temperature ( T C  > 500 °C) and excellent piezoelectric properties. However, a high leakage current was often detected in this system, which severely affects its applications. In this work, the 0.7BiFe (1− x ) Ga x O 3 -0.3BaTiO 3 (BFGa x -BT, 0.00 ≤  x  ≤ 0.10) system was designed to reveal the reason of leakage-current density decreased by their leakage mechanism. Because of the suppression of generation of Fe 2+ and oxygen vacancy ( ⁠ V O ∙ ∙ ⁠ ), the leakage mechanism from space charge limited conduction mechanism found in Ga-free BF-BT ceramics turns into Ohmic conduction and Schottky emission mechanism as Fe 3+ was replaced with Ga 3+ . A good combination of piezoelectric properties ( d 33  = 174 pC N −1 and k p  = 29%) and high Curie temperature ( T C  = 497 °C) was achieved in the BFGa0.06-BT ceramic owning the lowest leakage-current density. This work will provide the clues for preparing the high insulation and high piezoelectric performance BF-BT-based ceramics by suppressing the valence change of Fe 3+ and V O ∙ ∙ appearance.