One of the ways to increase pinning force in superconductors is to create small precipitates of secondary phases in the bulk matrix. The samples of superconductor Bi2.18Sr3-xCaxCu2O8 with different compositions have been decomposed according to the phase diagram of the BiO1.5-SrO-CaO-CuO system. The study showed that microstructure of samples and critical parameters were changed.