Resolving the mechanism of ferroelectricity in hexagonal barium titanate

Ferroelectric ceramics form critical components of contemporary electronic devices due to their technologically appealing electromechanical properties. The cubic perovskite BaTiO3 comprises one of the most renowned ferroelectrics, where co-operative displacements of the Ti4+ cations along the <111> lattice direction produce the macroscopic polarisation. BaTiO3 can also exist in a hexagonal polymorph (h-BaTiO3), which – despite also being ferroelectric – has attracted surprisingly little attention. Moreover, the mechanism of ferroelectricity in this material has remained contentious owing to its insufficient structural characterisation. We seek to resolve the controversy regarding its ferroelectric ground state by performing a variable-temperature synchrotron X-ray diffraction (S-XRD) study. This will inform how ferroelectric properties can be engineered into similar structural architectures, informing the design of multifunctional ceramic materials for future electronic devices.