Enhanced Energy Storage Density of Lead Lutetium Niobate Crystals by Electric Field-Induced Secondary Phase Transition via Na/La Codoping.

As emerging materials for capacitor applications, antiferroelectric (AFE) materials possess high energy storage density. AFE single crystals are conducive to studying the physical mechanism of AFE response. However, the preparation of AFE single crystals is a huge and long-standing challenge. Herein, we report the effect of Na/La codoping on the energy storage properties and phase transition of Pb(Lu1/2Nb1/2)O3 (PLN) AFE single crystals. An enhanced recoverable energy storage density of 4.81 J/cm3 with a high energy efficiency of 82.36% is obtained, which is much larger than that of the PbZrO3- and PLN-based AFE crystals. Two superlattice reflections, which stem from the A-site Pb2+ ions and the ordered B-site ions, are identified by X-ray diffraction and selected-area electron diffraction. The domain structures demonstrated a high temperature stability of the AFE phase. A secondary ferroelectric phase transition is induced after codoping, resulting in a sharp improvement of polarization (12.5 μC/cm2), which contributes to the enormous enhancement of energy storage density. This multiphase transition is explained using the modified Ginzburg-Landau-Devonshire phenomenology.