Lowering of BaB′1/3B″2/3O3 complex perovskite sintering temperature by lithium salt additions

Complex perovskite materials with the formula BaB′1/3B″2/3O3 have been broadly studied for their attractive dielectric properties. These materials exhibit a high relative dielectric constant and a very low dissipation factor. For example, the BaMg1/3Ta2/3O3 material has a relative dielectric constant close to 26 with a dissipation factor lower than 10−4 at 1 MHz. These properties are very promising for applications such as hyper-frequency resonators or/and capacitors. Unfortunately, a high temperature is necessary to achieve a satisfying densification of this materials family (>1400 °C) whereas the lowering of this temperature is more and more crucial from the industrial point of view. In particular, the development of Base Metal Electrodes Multi-Layer Ceramic Capacitors (BME-MLCC) requires the sintering of dielectric materials at low temperatures (<1100 °C). The aim of the study is thus to lower the sintering temperature of these materials. For this goal, lithium salts (Li2CO3, LiF, BaLiF3 and LiNO3) have been tested as sintering agents to densify BaZn1/3Ta2/3O3, BaMg1/3Ta2/3O3 and BaZn1/3Nb2/3O3 materials. It is shown, for example, that the BaMg1/3Ta2/3O3 sintering temperature is lowered by 300 °C when 15 mol % of lithium nitrate is added without affecting the dielectric properties at 1 MHz. For the best sintering agents investigated and each studied materials, the ceramic is characterised in terms of final density, microstructure and dielectric properties and densification mechanisms are discussed.