Relaxor or classical ferroelectric behaviour in ceramics with composition Ba1-xNaxTi1-xNbxO3

Ceramics with composition Ba1 - x Na-x Ti1 - x Nb-x O-3 are of either classical ferroelectric (for 0 less than or equal to x less than or equal to 0.075) and ferro- or antiferroelectric (for 0.55 < x less than or equal to 1) or relaxer ferroelectric type (for 0.075 less than or equal to x less than or equal to 0.55), the transition at T-c being only diffuse without any frequency dispersion for this last region. All the corresponding dielectric characteristics, i.e. diffusivity of the ferroelectric-paraelectric transition, frequency dispersion of epsilon(r)', shift of T-m with frequency deviation from the Curie-Weiss law, are determined. The relaxer behaviour is more relaxer the more the composition deviates from BaTiO3 and NaNbO3. This study is in the field of preparation of relaxer ceramics free from lead in the interest of the environment, which present a transition temperature dose to room temperature.