Tailoring Electrical Properties of BiFeO3-BaTiO3 Ceramics via A-site La3+ Substitution：Suppressed Leakage and Enhanced Strain

Abstract

To tailor the electrical properties of 0.7BiFeO3-0.3BaTiO3 (BFO-BTO) lead‑free ceramics, a series of A‑site La3+‑doped 0.7Bi1-xLaxFeO3-0.3BaTiO3 (x = 0, 0.01, 0.03, 0.05, 0.07) ceramics are synthesized using a sol-gel method combined with two-step sintering. The effects of La content on phase structure, defect chemistry, and dielectric, ferroelectric, and strain properties are systematically investigated. The results show that La3+ doping effectively suppresses Bi3+ volatilization, thereby reducing the concentrations of oxygen vacancies and Fe2+. The sample with x = 0.03 exhibits the lowest leakage current density together with the highest remanent polarization (Pr = 33.53 μC/cm2). When the doping level increases to x = 0.05, the system approaches a rhombohedral-pseudocubic morphotropic phase boundary (MPB), accompanied by pronounced lattice softening. Consequently, the dielectric constant, strain response, and equivalent piezoelectric coefficient d_33^* (297 pm/V) all reach their maximum values, while the coercive field decreases to a minimum (Ec = 22.2 kV/cm). However, excessive doping (x = 0.07) increases defect concentration again and disrupts phase structure, leading to deterioration of all the above-mentioned properties. This work provides clear compositional guidelines for selectively optimizing different functional properties of the material through a single dopant.