Anomalous piezoelectric response of ferroelectric mesocrystalline BaTiO3/Bi0.5Na0.5TiO3 nanocomposites designed by strain engineering

Abstract

Mesocrystals, a new class of unique materials, not only have potential properties based on the individual nanocrystals but also have a single-crystal-like function. Here, we report a ferroelectric mesocrystalline BaTiO₃/Bi_0.5Na_0.5TiO₃ (BT/BNT) nanocomposite synthesized from a layered titanate H_1.07Ti_1.73O₄ (HTO) by an ingenious two-step topochemical process for the first time. The BT/BNT nanocomposite is constructed from well-aligned BT and BNT nanocrystals with the same crystal-axis orientation. The BT/BNT heteroepitaxial interface in the nanocomposite is promising for an enhanced piezoelectric performance by using lattice strain engineering, which gives a giant piezoelectric response with a value of 408 pm V⁻¹. The introduced lattice strain at the BT/BNT heteroepitaxial interface causes transitions of pseudo-paraelectric BT and BNT nanocrystals to ferroelectric nanocrystals in the mesocrystalline nanocomposite, which enlarges ferroelectric, piezoelectric and dielectric responses. The lattice strain also results in the elevated Curie temperatures (T_c) of BT and BNT and a new intermediate phase transition.