DETERMINATION OF THE SOLUBILITY OF ALKALINE-EARTH METALS (CA, SR, BA) INTO LA2CUO4 BY THE SCFZ METHOD

Relations between the dopant contents in La2-xMxCuO4 (M = Ca, Sr, Ba) and the solvents of 78-80 mol% CuO and also the solubility of the dopants into La2CuO4 were investigated by the slow cooling floating zone method (SCFZ). The dopant content of La2-xMxCuO4 precipitated from the molten solvents increases as the dopant content of the solvents increases up to about 1.0. However, the contents of Ca and Sr in La2-xMxCuO4 are saturated at about 0.14 and 0.23, respectively, at a dopant content more than 1.0 in the solvents. The effective distribution coefficients k of the dopants into La2CuO4 are smaller than unity, and also k becomes smaller in the order of Sr, Ca and Ba. k(Sr) and k(Ca) decrease with dopant content in La2-xMCuO4 increasing, but k(Ba) is about 0.13 which is independent on the Ba content in La2-xBaxCuO4.