EN
YBa_{2}Cu_{3}O_{7-δ} (YBCO) bulk single-grain superconductors were prepared by a TSMG process. CeO_{2}, BaCeO_{3} and BaO_{2} powders were added to nominal composition Y_{1.5}Ba_{2}Cu_{3}O_{7} with the aim to refine Y_{2}BaCuO_{5} (Y-211) secondary particles. Added powders were refined by milling in a friction milling and characterized by X-ray powder difractometry. Thermal properties of the systems were characterized by DTA. Microstructure of samples was studied by PLM. Successful refinement of Y-211 particles size was confirmed by IP measurements. Transition temperatures and field dependences of the magnetic moment for further determination of the critical current densities were obtained using a VSM.