We have investigated the influence of Ca-substitution and different rare earths on the microstructure of RE1-x
(RE= Y, Eu, Er; x=0, 0.2, 0.3) superconducting ceramics. Scanning electron microscopy, X-ray microanalysis and energy dispersive spectroscopy have been used to study the microstructure and the chemical composition of the samples. A correlation was established between the polycrystalline microstructure and phase formation depending on the additive content. We observed that calcium is distributed uniformly in the crystals. The formation of minor impurity phases improved the sintering conditions.