The first oxyfluoride ferroelectric relaxor

A fine dielectric study of the BaTiO3-BaLiF3 system has shown that ceramics with composition Ba(Ti1-xLix)O3-3xF3x present two different behaviour: a classical ferroelectric one for (0 less than or equal to x less than or similar to 0.04), a ferroelectric relaxer one for (0.04 less than or similar to x less than or similar to 0.15). Such materials constitute the first oxyfluoride ferroelectric relaxors with corresponding typical dielectric characteristics: diffuse phase transition, frequency dispersion, increase of T-m (temperature of the maximum of epsilon(r)') with frequency, deviation from the Curie-Weiss law. The occupation of the same crystallographic sites by heterovalent cations (Ti4+, Li+) and anions (O2-, F-) is the cause of such properties.