[en] This thesis concerns the preparation and characterization of cuprate based high-T_c superconductors (Y-123 and Bi-2223) and especially development and testing of BaZrO₃ based materials. The formation of YBa₂Cu₃O_y (Y-123) by a CO₂-free route involving reaction sintering of stoichiometric mixtures of chemically prepared fine powders of Y₂BaCuO₅, BaCuO₂ and CuO have been studied by thermal and XRD analysis. The synthesis and sintering of BaZrO₃ powders prepared by the hydroxide-alkoxide-methanol sol-gel route have been studied. The phase relations in the system BaO-Y₂O₃-ZrO₂ have been studied to determine the solid solubility limits for the perovskite phase Ba_XY_YZr_ZO_N (X+X+Z=3) at 1500 deg. C. In the binary system Y₂O₃-BaZrO₃ the solubility limit was found to be ≅19 mol% Y₂O₃, i.e. Ba_0.81Y_0.4₂Zr_0.81O₃. along the joint BaYO_2.5-Ba the boundary was determined to be at BaY_0.21Zr₀.₇₉O_2.895. evidence for a new solid solution series between Ba₃Y₄O₉ and ZrO₂ are given, and a partial 1500 deg. C phase diagram for the ternary system BaO-Y₂O₃-ZrO₂ is presented. The growth of BaZrO₃ single crystals have been attempted both by a laser zone floating technique and flux methods. The compatibility between YBa₂Cu₃O₇-X and BaZrO₃, Ba_XY_YZr_ZO_3-δ as well as BaHfO₃ have been studied at 950 deg. and 1050 deg. C. The results show the four most promising candidates as support materials for fabrication of YBa₂Cu₃O_y to be BaHfO₃, BaY_0.05Zr_0.95O_2.975, , BaZrO₃ and BaY_0.1Zr_0.9O_2.95. (EG)