Dielectric, impedance and piezoelectric properties of (Na_0.5La_0.5)TiO₃-doped 0.67BiFeO₃–0.33BaTiO₃ ceramics

The crystallographic structure, dielectric, impedance and piezoelectric properties of novel (0.67 − x)BiFeO₃–0.33BaTiO₃–x(Na_0.5La_0.5)TiO₃ (NLT100x, x = 0.0, 0.02, 0.04, 0.06, 0.08) ceramics were systematically investigated experimentally. The crystallographic studies showed that different concentrations (Na_0.5La_0.5)TiO₃ doping were well soluble with the BiFeO₃ system to form a single pseudo-cubic phase solid solution. The dielectric analysis shows that the doping reduces the leakage current, suppresses the Bi volatilization, expands the dielectric peak, and leads to the evolution of relaxor behavior. Moreover, the large strain (S) of 0.255% and the normalized strain of 430 pm/V were obtained at x = 0.04 and 60 kV/cm, which is attributed to the coexistence of ferroelectric and relaxor domains favoring the domain steering. More importantly, raising the temperature can further improve the strain performance, reaching the maximum strain (S_max) value (~ 0.346%) with the maximum normalized strain of (~ 714 pm/V) at 120 °C and 50 kV/cm. The results show the potential value of the ceramics in piezoelectric actuator applications.