The grain size effect on dielectric properties of BaTiO3 based ceramics

In response to the demand for small grain size in thin dielectric layers of multilayer chip capacitors (MLCC), ultrafine powders were synthesized by chemical method. Using the high purity BaTiO3 powders of various grain sizes, temperature-stable dielectric materials of the specification 'X7R' were prepared. The effects of the grain size of starting BaTiO3 powders, modifier and sintering temperature on the dielectric properties were investigated. The ceramic grain size was almost proportional to the particle size of the starting BT powders. Sintering below 1280 degreesC, the ceramics with an average grain size less than 500 nm were obtained, showing a high dielectric constant up to 4150 and temperature coefficient of capacitance (TCC) less than +/-15%, which meets the requirement of X7R specification. (C) 2002 Elsevier Science B.V. All rights reserved.