Phase assemblage was investigated in the Bi-Sr-Ca-Cu-Sn-O system at temperatures of Bi-2212 phase crystallization. It is found that the Sr_1-x Ca_x SnO₃ phase (x = 0.1-0.2) is compatible with Bi-2212 as well as with Bi-2201, CuO, alkaline-earth metal cuprates and bismuthates. The solubility of Sn in Bi-2212 is limited to low values. The superconducting composites Bi-2212-(Sr, Ca)SnO₃ were prepared by melt crystallization using single precursor and mixed precursor routes. The materials consisted of Bi-2212 matrix with submicron (Sr, Ca)SnO₃ grains included in Bi-2212 lamellas and agglomerated in between. The composites exhibited enhanced flux pinning at T = 60 K, while at 5 K the effect of (Sr, Ca)SnO₃ addition was not revealed.