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 t he citrate method and titanium isopropoxide as a starting material. After d rying and calcining, the titanyl citrate gels were converted into powders o f lanthanum oxide doped strontium titanate. The cation ratios of the titana te 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 w ere precipitated using either ethanol or acetone. The precipitates obtained using acetone were always of a slimy consistency whereas those obtained us ing a sufficient quantity of alcohol were powdery. The powder obtained at p H 5-6 consisted of fine particle with a diameter of 0.3-0.5 mu m and sinter ed readily between 1250 and 1350 degrees C. The dielectric constants of the semiconducting La2O3-doped strontium titanates were determined. (C) 2000 E lsevier Science Ltd and Techna S.r.l. All rights reserved.