Nonhydrolytic sol–gel synthesis and dielectric properties of ultrafine-grained and homogenized Ba0.70Sr0.30TiO3

A simple process has been investigated to synthesize nanocrystalline Ba0.70Sr0.30TiO3 (BST) powders via a nonhydrolytic sol–gel method by using barium acetate, strontium acetate, titanium tetrabutoxide, ethanol, acetic acid and acetylacetone as the starting materials. Thermogravimetry (TG) and differential thermal analysis (DTA) were used to examine the decomposition behaviour of the xerogel. The particle size of BST is close to 30 nm calculated by X-ray diffraction (XRD) and confirmed by transmission electron microscopy (TEM). Using these nanocrystalline BST powders, dense BST ceramics with ultrafine grains were obtained by spark plasma sintering (SPS). The grain size effect on the dielectric properties was studied. It was shown that as the grain size decreased, the transition temperature (Tc) and the dielectric constant decreased and the transition became diffuse.