Energy storage and photoluminescence properties of Sm<sup>3+</sup>-doped 0.94Bi<sub>0.5</sub>Na<sub>0.5</sub>TiO<sub>3</sub>-0.06BaTiO<sub>3</sub> multifunctional ceramics

Abstract

In recent years, inorganic multifunctional ferroelectric ceramics have been widely utilized in various fields, including aerospace, optical communication, and capacitors, owing to their high stability, easy synthesis, and flexibility. Rare-earth doped ferroelectric materials hold immense potential as a new type of inorganic multifunctional material. This work focuses on the synthesis of <i>x</i>%Sm<sup>3+</sup>-doped 0.94Bi<sub>0.5</sub>Na<sub>0.5</sub>TiO<sub>3</sub>-0.06BaTiO<sub>3</sub> (BNTBT:<i>x</i>%Sm<sup>3+</sup> in short) ceramics by using the conventional solid-state sintering method, aiming to comprehensively investigate their ferroelectric, energy storage, and photoluminescence (PL) properties. The X-ray diffraction analysis reveals that the introduction of Sm<sup>3+</sup> does not trigger off the appearing of secondary phases or changing of the original perovskite structure. The scanning electron microscope (SEM) images demonstrate that Sm<sup>3+</sup> incorporation effectively restrains the grain growth in BNTBT, resulting in the average grain size decreasing from 1.16 to 0.95 μm. The reduction in remanent polarization (<i>P</i><sub>r</sub>) and coercive field (<i>E</i><sub>c</sub>) can be attributed to both the grain size refinement and the formation of morphotropic phase boundaries (MPBs). Under an applied field of 60 kV/cm, the maximum value of energy storage density (<i>W</i><sub>rec</sub>) reaches to 0.27 J/cm<sup>3</sup> at an Sm<sup>3+</sup> doping concentration of 0.6%. The energy storage efficiency (<i>η</i>) gradually declines with electric field increasing and stabilizes at approximately 45% for Sm<sup>3+</sup> doping concentrations exceeding 0.6%. This result can be ascribed to the decrease in Δ<i>P</i> (<i>P</i><sub>max</sub><sub> </sub>– <i>P</i><sub>r</sub>) due to the growth of ferroelectric domains as the electric field increases. Additionally, all Sm<sup>3+</sup>-doped BNTBT ceramics exhibit outstanding PL performance upon being excited with near-ultraviolet (NUV) light at 408 nm, without peak position shifting. The PL intensity peaks when the Sm<sup>3+</sup> doping concentration is 1.0%, with a relative change (Δ<i>I/I</i>) reaching to 700% at 701 nm (<sup>4</sup>G<sub>5/2</sub>→<sup>6</sup>H<sub>11/2</sub>). However, the relative change in PL intensity is minimum at 562 nm (<sup>4</sup>G<sub>5/2</sub>→<sup>6</sup>H<sub>5/2</sub>) due to the fact that the <sup>4</sup>G<sub>5/2</sub>→<sup>6</sup>H<sub>5/2</sub> transition represents a magnetic dipole transition, and the PL intensity remains relatively stable despite variations in the crystal field environment surrounding Sm<sup>3+</sup>. Our successful synthesis of this novel ceramic material, endowed with both energy storage and PL properties, offers a promising avenue for developing inorganic multifunctional materials. The Sm<sup>3+</sup>-doped BNTBT ceramics hold considerable potential applications in optical memory and multifunctional capacitors.