Malonate salts of the above metals dissolved in a glycerol/malonic acid polyester have been found to form amorphous oxide systems at relatively low temperatures. Mixtures of the appropriate stoichiometry rapidly form the corresponding 2212 BSCCO and tetragonal YBCO oxide systems on heating to temperatures in the range 750-850 degrees C. In the case of YBCO, the formation of crystalline barium carbonate can be largely suppressed by an appropriate thermal programme, but whereas the tetragonal YBCO6.5 phase can be readily obtained as the sole crystalline phase, oxygen diffusion into this phase is remarkably difficult. This appears to be due to the presence of amorphous intergranular material.