Size effect of barium titanate based ceramics sintered in reducing atmospheres

Non-reducible BT-based X7R type ceramic materials with grain size form 100 nm to 400 nm were prepared systematically with high performance using nano-sized BaTiO₃ powders. The initial grain size of BT powders affects significantly the microstructure and dielectric properties. The dielectric constant could be enhanced by increasing the initial particle size. Using BT powder with size of 250 nm, high density BME-MLCC chip samples (ceramic grain size of 300 nm) were obtained sintered at 1217°C, exhibiting high dielectric constant above 3000, and TCC less than ± 11.5%. with good reliability, meeting the requirement of X7R specification. In nanoceramic X7R BaTiO₃ sample, clear ferroelectric domain structure was also observed for the first time. The inhomogeneous core-shell microstructure was found in the X7R samples.