Nb-doped BaTiO3-(Bi0.5Na0.5)TiO3 ceramics with core-shell structure for high-temperature dielectric applications

Nb-doped 0.90BaTiO(3)-0.10(Bi0.5Na0.5)TiO3 temperature-insensitive ceramics with novel core-shell structure were sintered at low temperature by the conventional solid-state reaction method. The beneficial role of Nb in facilitating the formation of core-shell structure because of chemical inhomogeneity is verified, which is responsible for the weak temperature dependence of dielectric properties. Temperature dependence of permittivity measured at different frequencies shows high frequency dispersion at low temperature, while without relaxor characteristic at high temperature. The Vogel-Fulcher model was adopted to study the relaxor behaviour of Nb-doped 0.90BaTiO(3)-0.10(Bi0.5Na0.5)TiO3 ceramics at low temperature. The samples with an addition of 1.5 mol% Nb2O5 provide a temperature coefficient of capacitance meeting the requirements of the X9R characteristic, and result exhibits an optimum dielectric behaviour of epsilon(r) similar to 1900, tan delta similar to 1.8% at room temperature, making the material a promising candidate for high temperature applications.