The Sintering Behavior And Doping Modification Of Strontium Barium Niobate Ceramics

Due to its excellent pyroelectric, electro-optic and photo-refractive properties, strontium barium niobate (SBN) is one of the most potential lead-free ferroelectric materials. For SBN crystal, high cost and difficult fabrication process have seriously hampered its practical application in various fields. And SBN ceramics, with advantages of low cost and easy fabrication, has drawn more and more attention. However, high-density SBN ceramics are difficult to obtain because of the abnormal grain growth. The purpose of this investigation is to study how to avoid the abnormal grain growth caused by local liquid phase and improve the density and dielectric properties. Ce^3+.doped and undoped Sr_0.5Ba_0.5Nb₂O₆ ceramics were sintered with amorphous SiO₂ as the sintering additive. The effects of SiO₂ and Ce³⁺ on the sintering behaviors, microstructure and dielectric properties were studied.With the increasing amounts of silica, the sintering active energies decreased and sintering time was shorten. In the same sintering conditions, the dielectric properties were improved and the degree of diffuse phase transition was weakened for the improved densities and increasing grain sizes. With the help of the additive of 1.5wt%, the relative density of samples reached to 96.3%, and the dielectric constant was up to -4322, which was twice as much as other results already reported. It suggested that the amorphous SiO₂ was an effective sintering additive in improving the sintering behavior and dielectric properties.The results also indicated that Ce³⁺ ions did not entirely enter the crystal lattice after the powder calcination. The remains lying in the grain boundary entered the lattice during the sintering process. Compared with sintering additive, the effect of Ce³⁺ ions on the sintering active energy was so slight that it could be negligible when the amount of SiO₂ reached 1.5wt%. However, Ce³⁺ doping could suppress the grain growth and reduce the grain size even though the amount of silica was up to 1.5wt%.In this study, SBN ceramics with a wide sintering range, uniform microstructure and excellent dielectric properties were prepared with low-cost raw materials and simple technology, which has good prospects for practical application.