Structurally frustrated polar nanoregions in BaTaO2N and the relationship between its high dielectric permittivity and that of BaTiO3

This letter presents direct evidence for the existence of the same inherently polar one-dimensional (1D), displacive disorder in BaTaO2N as occurs in paraelectric BaTiO3 as well as in doped BaTiO3 relaxor ferroelectric systems. The inherently polar, off-center and oppositely directed displacements of Ta and neighboring O/N ions along < 001 > give rise to 1D polar nanoregions (PNRs) and are responsible for the dielectric properties of BaTaO2N. A bond valence sum analysis of the underlying crystal chemistry of BaTaO2N shows clearly that O/N ordering is not directly responsible for inducing the observed 1D PNRs. (c) 2008 American Institute of Physics.