Tetragonal Distortion of a BaTiO3/Bi0.5Na0.5TiO3 Nanocomposite Responsible for Anomalous Piezoelectric and Ferroelectric Behaviors

Ferroelectric mesocrystalline nanocomposites are functional materials with improved ferroelectricity via lattice strain engineering. In this study, X-ray diffraction (XRD) and soft X-ray absorption spectroscopy (XAS) are performed to determine the tetragonal distortion of Bi 0.5 Na 0.5 TiO 3 (BNT) in a ferroelectric mesocrystalline BaTiO 3 (BT)/BNT nanocomposite. The XRD results demonstrate the expansion of the BNT lattice in the BT/BNT nanocomposite. Using Williamson-Hall analysis, the tensile strain of BNT in BT/BNT-700 is confirmed. Shift and splitting of the e g orbital are observed for BNT in the BT/BNT nanocomposite in Ti L 3 -edge XAS, suggesting the lower symmetry of the TiO 6 octahedron in BNT, which is ascribed to a significant tetragonal distortion of BNT in the BT/BNT nanocomposite caused by the lattice mismatch between BNT and BT. It is found that the tetragonally distorted BNT in BT/BNT is responsible for the anomalous ferroelectric response of the mesocrystalline BT/BNT nanocomposite.