Enhanced energy density with a wide thermal stability in epitaxial Pb_0.92La_0.08Zr_0.52Ti_0.48O₃ thin films

High-quality epitaxial Pb_0.92La_0.08Zr_0.52Ti_0.48O₃ (PLZT) films of thickness of ∼880 nm were fabricated using pulsed laser deposition on (001) Nb doped SrTiO₃ (Nb:STO) substrates. Besides a confirmation of the epitaxial relationship [100]_PLZT//[100]_Nb:STO and (001)_PLZT//(001)_Nb:STO using X-ray diffraction, a transmission electron microscopy study has revealed a columnar structure across the film thickness. The recoverable energy density (W_rec) of the epitaxial PLZT thin film capacitors increases linearly with the applied electric field and the best value of ∼31 J/cm³ observed at 2.27 MV/cm is considerably higher by 41% than that of the polycrystalline PLZT film of a comparable thickness. In addition to the high W_rec value, an excellent thermal stability as illustrated in a negligible temperature dependence of the W_rec in the temperature range from room temperature to 180 °C is achieved. The enhanced W_rec and the thermal stability are attributed to the reduced defects and grain boundaries in epitaxial PLZT thin films, making them promising for energy storage applications that require both high energy density, power density, and wide operation temperatures.