Improved Non-Piezoelectric Electric Properties Based on La Modulated Ferroelectric-Ergodic Relaxor Transition in (BiNa)TiO-Ba(Ti, Zr)O Ceramics.

The characteristic transition from ferroelectric (FE) to ergodic relaxor (ER) state in (BiNa)TiO (BNT) based lead-free ceramics provides an efficient approach to bring a highly ordered phase back to a disordered one. It would be rational to utilize this transition to improve relevant non-piezoelectric properties based on domain decomposition. In this work, different La contents were introduced to 0.93(BiNa)TiO-0.07Ba(TiZr)O ceramics (BNT-BZT-La) to induce evolution of ergodic degree. The results reveal that with increasing La content, both the FE-ER transition temperature and depolarization temperature shift towards room temperature, implying a deepened ergodic degree. By modulation of ergodic degree, thermally stimulated depolarization current experiment shows a higher current density peak, and corresponding pyroelectric coefficient increases from 2.46 to 2.81 μC/(cm∙°C) at . For refrigeration, the indirect measurement demonstrates the Δ maximum increases from 1.1 K to 1.4 K, indicating an enhanced electrocaloric effect. Moreover, the optimized energy storage effect is observed after La doping. With appearance of "slimmer" - loops, both calculated recoverable energy storage density and storage efficiency increase to 0.23 J/cm and 22.8%, respectively. These results denote La doping conduces to the improvement of non-piezoelectric properties of BNT-based ceramics in a certain range. Therefore, La doping should be an adopted modification strategy for lead-free ceramics used in areas like refrigerator and pulse capacitors.