Preparation and characterization of coprecipitates and mechanical mixtures of calcium-strontium oxalates using XRD, SEM-EDX and TG

Abstract

In view of the study of the chemistry of the oxalate coprecipitation process for preparing BiSrCaCuO superconductors, the characteristics of oxalates of calcium and strontium in the Ca(NO3)(2)-Sr(NO3)(2)-HNO3-H2O-(NH4)(2)C2O4 system are investigated. Based on XRD, SEM and TG a comparison between the crystal structure, morphology and thermal decomposition behavior of coprecipitated and physically mixed calcium and strontium oxalates with the same Ca/Sr stoichiometry is made. It is shown that the coprecipitated powders form homogeneous solid solutions of which the crystal structure, morphology and thermal behaviour depend on the Ca/Sr stoichiometry. (C) 1998 Elsevier Science B.V.