The lower conductivity of Bi(Ga, Fe)O ₃ – x PbTiO ₃ ceramics near the morphotropic phase boundary

BiFeO ₃ –PbTiO ₃ (BF–PT) piezoelectric ceramics have attracted much attention due to the high Curie temperature [Formula: see text] of above 650°C in the vicinity of the morphotropic phase boundary (MPB). The reduction of leakage conduction is essential for practical applications of ceramics. In this paper, Bi(Ga[Formula: see text]Fe[Formula: see text])O ₃ –xPbTiO ₃ (BGF–xPT, [Formula: see text], 0.3, 0.35 and 0.45) ceramics were prepared by the conventional solid-state reaction routes. It has been found that BGF–xPT ceramics for [Formula: see text] and 0.35 have mixed perovskite phases with dominated rhombohedral (R) and tetragonal (T) phases, respectively, exhibiting refined grains with a size of 0.5–1.0 [Formula: see text]m. The enhanced dielectric constant and reduced dielectric loss as low as 0.02 at 100 Hz were achieved for [Formula: see text] and 0.35 ceramics. According to the impedance analysis, the mixed-phase ceramics of [Formula: see text] and 0.35 have relatively high resistance at 200°C, and the T-phase-dominated [Formula: see text] ceramics maintain higher resistance up to 420°C. The enhanced insulation properties of mixed-phase ceramics are dominated by the grain response with a relatively high activation energy of above 1 eV. The XPS analysis further indicates that the Bi/Pb volatility and Fe-valence fluctuation were suppressed in the mixed-phase ceramics. Our results indicate that the phase structural and defect-chemical regulation are beneficial to the enhancement of electrical insulation and thus piezoelectric properties of BF–PT-based ceramics.