Microstructure and dielectric properties of BaTiO₃-based X7R ceramics

Abstract

The relationship between the microstructures and dielectric properties of BaTiO₃-based X7R ceramics has been investigated at different calcination temperatures. The XRD and SEM results show that calcinations of BaTiO₃ raw powders increase the grain size and stabilize the tetragonality (c/a ratio) of the ceramics. The grain growth caused by the calcination prevents the doped ions from diffusing into the interior of the grains, and then increases the volume fraction of the tetragonal phased core. This process greatly increases the dielectric constant by improving the ferroelectricity. As a result, the relaxation mechanism of the domain reorientation generates high loss tangent. The BaTiO₃ ceramics with X7R specifications were prepared at the calcination temperature of 1200 °C and the sintering temperature of 1240 °C, whose dielectric properties were ɛ _r ≥ 4500, Δɛ _r/ɛ _r25 ≤  ± 10%(−55∼125 °C), tanδ ≤ 0.012(25 °C), respectively.