Although BaTiO3 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 BaTiO3 but is not efficient enough. Here, we report
a promoted chemical pressure route to prepare high-performance BaTiO3 films, achieving the highest remanent polarization, P
r (100 μC/cm2), to date and
high Curie temperature, T
c (above 1000
°C). The negative chemical pressure (∼−5.7 GPa)
was imposed by the coherent lattice strain from large cubic BaO to
small tetragonal BaTiO3, generating high tetragonality
(c/a = 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 eg 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.