Sintering of cerium oxide is difficult due his reduction to Ce₂O₃ with an oxygen elimination accompanied by the pores formation. Due to this phenomena in composition of samples uses some addives which limits this effect. In this paper two types of samples were synthesized. The first of these has stoichiometric composition corresponding to binary compound SrCeO₃. The second type of samples content 5 and 10% SrO respectively. The samples were thermally treated in the range 1250-1500^°C and were studied the mechanisms formation of compounds based on the obtained results by X-ray diffraction. At SrCeO₃ synthesis it observed that due reduction CeO₂ to Ce₂O₃ an intermediate phase Sr₂Ce₂O₅ was identified, this later compound being incongruent in solid phase. For a low SrO amount this compound not formed and SrCeO₃, which is an equilibrium phase, penetrates in CeO₂ network with the formation of a solid solution with fluorite structure. The microstructure of studied samples was examined by SEM microscopy.