Chemical-Pressure-Modulated BaTiO 3 Thin Films with Large Spontaneous Polarization and High Curie Temperature

Although BaTiO is one of the most famous lead-free piezomaterials, it suffers from small spontaneous and low Curie temperature. Chemical pressure, as a mild way to modulate the structures and properties of materials by element doping, has been utilized to enhance the ferroelectricity of BaTiO but is not efficient enough. Here, we report a promoted chemical pressure route to prepare high-performance BaTiO films, achieving the highest remanent polarization, (100 μC/cm ), to date and high Curie temperature, (above 1000 °C). The negative chemical pressure (∼-5.7 GPa) was imposed by the coherent lattice strain from large cubic BaO to small tetragonal BaTiO , generating high tetragonality ( / = 1.12) and facilitating large displacements of Ti. Such negative pressure is especially significant to the bonding states, i.e., hybridization of Ba 5p-O 2p, whereas ionic bonding in bulk and strong bonding of Ti e and O 2p, which contribute to the tremendously enhanced polarization. The promoted chemical pressure method shows general potential in improving ferroelectric and other functional materials.