Influence of A-site isovalent doping on structural and electrical properties of Bi-based lead-free piezoelectric ceramics

To understand the effects of A-site isovalent doping on the electrical properties of Bi-based lead-free piezoelectric ceramics, Bi0.47-xLaxNa0.47Ba0.06TiO3 with x = 0.00, 0.01, 0.03, and 0.05 were studied. All samples were fabricated by a conventional solid-state reaction method. The X-ray diffraction and the Rietveld refinement patterns of the samples show the Pm3m cubic phases. All sintered samples show dense microstructures and clear grain boundaries. The addition of La3+ decreases the average grain sizes of Bi0.47-xLaxNa0.47Ba0.06TiO3 samples from 1.039 μm for x = 0.00 to 0.831 μm for x = 0.05. The dielectric losses of samples are below 7% up to 400 °C at different frequencies. The temperature-dependent dielectric curves of poled Bi0.47-xLaxNa0.47Ba0.06TiO3 samples confirm a phase transition from a nonergodic relaxor to an ergodic relaxor phase when x ≥ 0.03. Interestingly, the composition near the phase transition region, Bi0.44La0.03Na0.47Ba0.06TiO3, shows a maximum strain of ~ 0.356% at a low applied electric field of 5 kV/mm, showing a potential lead-free candidate for piezo actuator applications.