The Effect of Silver on the Microstructure and Dielectric Property of BaTiO3

In the present study, a solid-state reaction technique is used to prepare the barium titanate powders with different Ba/Ti ratios. The calcination was carried out at 1100℃ for 2h. The non-stoichiometric BaTiO3 samples were sintered at various temperatures in air. The effects of Ba/Ti ratio on the sintering behavior, microstructures and dielectric properties are investigated. In the present study, Ag is doped into the non-stoichiometric BaTiO3. The Ag-containing BaTiO3 was sintered in air at different temperature. The influence of the Ag powders on the dielectric properties and microstructure of the non-stoichiometric BaTiO3 is investigated.
In the Ba-rich system, a small amount of Ba2TiO4 is found in the Ba-rich system. The presence of Ba2TiO4 phase inhibits densification, the grains exhibit equiaxis shape. However, the density of the Ba-rich specimen is low. In the Ti-rich system, Ba6Ti17O4 phase is found, indicating the presence of a liquid phase during sintering while the temperature is higher than the eutectic temperature (1320℃). The presence of the liquid phase enhances the densification, and abnormal grains are also formed. The dielectric constant of the Ti-rich BaTiO3 is thus degraded.
While doping silver into BaTiO3, a small amount of silver can increase the amount of abnormal grain and its size. When the silver content is higher than the solubility, the silver inclusions can inhibit the coarsening of BaTiO3. There are some replacements of Ba2+ with Ag+. The dielectric constant and relative density depend strongly on silver content and sintering temperature above or below eutectic point. The Ag solubility in Ti-rich BaTiO3 is higher than that in Ba-rich BaTiO3.