Improved Non-Piezoelectric Electric Properties Based on La Modulated Ferroelectric-Ergodic Relaxor Transition in (Bi0.5Na0.5)TiO3-Ba(Ti, Zr)O3 Ceramics

Abstract

The characteristic transition from ferroelectric (FE) to ergodic relaxor (ER) state in (Bi0.5Na0.5)TiO3 (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(Bi0.5Na0.5)TiO3-0.07Ba(Ti0.945Zr0.055)O3 ceramics (BNT-BZT-xLa) to induce evolution of ergodic degree. The results reveal that with increasing La content, both the FE-ER transition temperature TF-R and depolarization temperature Td 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/(cm2∙°C) at Td. For refrigeration, the indirect measurement demonstrates the ΔT 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” P-E loops, both calculated recoverable energy storage density Wrec and storage efficiency η increase to 0.23 J/cm3 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.

High-Energy Storage Properties over a Broad Temperature Range in La-Modified BNT-Based Lead-Free Ceramics

“…In addition, the samples exhibit an ultra-short t 0.9 (corresponding to a discharge time of 90% of the saturated W d value), which is 89 ns for the CS-sintered sample and 75 ns for the TSS-sintered sample. Both values are significantly lower than those in many other energy storage materials. ,,,− The fast discharge rate of the 0.12La sample indicates that the material can release stored energy in a very short time, demonstrating its good application value. In addition, when comparing the charging and discharging performance between the CS- and TSS-sintered samples, the TSS-sintered sample exhibits a higher discharge rate, which can be related to its high energy storage efficiency.…”

“…Unlike linear and ferroelectric ceramics, relaxor ferroelectric ceramics generally have high P max , low P r , and moderate BDS, the characteristics that more likely provide high energy storage density. , Considering that the vast majority of traditional relaxor ferroelectric ceramics are lead-based materials detrimental to humans and the environment, research and development of lead-free energy storage materials have intensified in recent years. ,, Lead-free (Bi 0.5 Na 0.5 )­TiO 3 (BNT) ceramic is an important kind of relaxor ferroelectric ceramics, exhibiting a high dielectric constant and strong ferroelectricity. − However, low BDS and large hysteresis with high P r hinder their energy storage applications. Common approaches for improving the energy storage performance of BNT-based materials are phase adjustment along with domain engineering and grain size control via doping or employing different processing methods.…”

“…La 3+ ions are a common dopant of lead-free piezoelectric ceramics. For BNT-based ceramics, the long-range ferroelectric order was disturbed significantly via La 3+ doping, increasing the degree of ergodicity. − Meanwhile, La 3+ acts as a grain growth inhibitor for BNT-based ceramics, suppressing the grain growth during sintering. ,, Therefore, based on the above reasons, La 3+ doping is expected to improve the energy storage properties of BNT-based ceramics. In addition to suitable dopants, the base composition is also critical for obtaining optimal energy storage performance.…”

Effect of La substitution on energy storage properties of (Bi0.2Na0.2Ca0.2Ba0.2Sr0.2)TiO3 lead‐free high‐entropy ceramics

“…27 In addition, the long-range ferroelectric order can be severely disrupted through La doping, which will contribute to the promotion of ergodicity degree and energy storage performance. [28][29][30][31] Zhang et al reported that the ergodic degree deepened with La content in a La-doped 0.93(Na 0.5 Bi 0.5 )TiO 3 -0.07Ba(Zr 0.055 Ti 0.945 )O 3 system, which resulted in "slimmer" P-E loops and enhanced η and W rec . 29 Yu et al added La to 0.78Na 0.5 Bi 0.5 TiO 3 -0.22K 0.5 Bi 0.5 TiO 3 ceramics and discovered that the ferroelectric order was largely disrupted by La doping and converted to an ergodic relaxation state.…”

“…[28][29][30][31] Zhang et al reported that the ergodic degree deepened with La content in a La-doped 0.93(Na 0.5 Bi 0.5 )TiO 3 -0.07Ba(Zr 0.055 Ti 0.945 )O 3 system, which resulted in "slimmer" P-E loops and enhanced η and W rec . 29 Yu et al added La to 0.78Na 0.5 Bi 0.5 TiO 3 -0.22K 0.5 Bi 0.5 TiO 3 ceramics and discovered that the ferroelectric order was largely disrupted by La doping and converted to an ergodic relaxation state. 30 In summary, the energy storage properties of lead-free ferroelectrics can be optimized by La doping.…”