Nb-Doped 0.9BaTiO3-0.1(Bi0.5Na0.5)TiO3 Ceramics with Stable Dielectric Properties at High Temperature

Nb-doped 0.9BaTiO(3)-0.1Bi(0.5)Na(0.5)TiO(3) (0.9BT-0.1BNT) ceramics were prepared by conventional solid-state method. The dielectric and the structural properties were investigated. It was found that the temperature-capacitance characteristics greatly depended on Nb2O5 content. With the addition of 2.0 mol% Nb2O5, 0.9BT-0.1BNT ceramic sample could satisfy the EIA X9R specification. This material was promising for high-temperature MLCC application. Microstructure element distribution was studied using TEM and EDS. The Bi and Na were almost homogeneously distributed except grain-boundary segregation of Bi. The Nb exhibited a nonuniform distribution from the grain boundary to the interior, showing the simultaneous presence of Nb-rich and Nb-poor regions. Such microheterogeneity gave rise to the temperature stability of permittivity. The solution-precipitation mechanism was introduced to elucidate the evolution of microstructures. Degradation and recovery of insulation resistance were observed under a dc bias at 200 degrees C, which was attributed to the electro-migration and diffusion of Na+.