MORPHOLOGY AND THERMAL-DECOMPOSITION BEHAVIOR OF COPRECIPITATED LA-BU-CU OXALATE

The morphology and thermal decomposition behavior of coprecipitated La -Ba-Cu oxalate have been investigated. It was found that La-Ba-Cu copr ecipitates first decompose into CuO, BaCO3 and La2O2CO3; then La2O2CO3 reacts with some CuO to form La2CuO4. Thereafter, La2CuO4, BaCO3 and residual CuO react together to form the solid-solution phase of LaBa2C u3Oy, i.e., La1+xBa2-xCu3Oy (0<x<0.5) and BaCuO2. Single-phase LaBa2Cu 3Oy could be synthesized by heating the calcined Powders at 880-degree s-C for 6 h in N2 atmosphere. Coarse La2(C2O4)3-based particles, on wh ose surfaces Ba ions were adsorbed, were found in the coprecipitates. The high calcination temperature is due to the inhomogeneity of the co mposition and particle morphology. A coarsening mechanism of the parti cles is also suggested.