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

Ceramics with composition Ba 1- x Na x Ti 1- x Nb x O 3 are of either classical ferroelectric (for 0 ⩽ x < 0.075) and ferro- or antiferroelectric (for 0.55 < x ⩽ 1) or relaxor ferroelectric type (for 0.075 ⩽ x ⩽ 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 ε' r , shift of T m with frequency deviation from the Curie-Weiss law, are determined. The relaxor behaviour is more relaxor the more the composition deviates from BaTiO 3 and NaNbO 3 . This study is in the field of preparation of relaxor ceramics free from lead in the interest of the environment, which present a transition temperature close to room temperature.