Relaxor or classical ferroelectric behaviour in ceramics with composition Ba_1-xNa_xTi_1-xNb_xO₃

Ceramics with composition Ba_1-xNa_xTi_1-xNb_xO₃ 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 BaTiO₃ and NaNbO₃. 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.