Preparation and dielectric properties of semiconducting lanthanum-doped strontium titanate ceramics from titanyl citrate precursors

This study deals with the preparation of titanyl citrate precursors using the citrate method and titanium isopropoxide as a starting material. After drying and calcining, the titanyl citrate gels were converted into powders of lanthanum oxide doped strontium titanate. The cation ratios of the titanate powder prepared at pH 5–6 were very close to the original one. Only less than 0.1% of free cations remained in the solution. The titanyl citrates were precipitated using either ethanol or acetone. The precipitates obtained using acetone were always of a slimy consistency whereas those obtained using a sufficient quantity of alcohol were powdery. The powder obtained at pH 5–6 consisted of fine particle with a diameter of 0.3–0.5 μm and sintered readily between 1250 and 1350°C. The dielectric constants of the semiconducting La2O3-doped strontium titanates were determined.