REACTIONS BETWEEN YBA2CU3O7-DELTA AND OXIDES OF FE, CO AND ZN

Solid state reactions between YBa2Cu3O7-delta and oxides of Me=Fe, Co and Zn, mixed in various molar ratios r=MeO(n)/YBa2Cu3O7-delta, were s tudied at 925-degrees-C in air. The reaction products were characteriz ed by X-ray powder diffraction and SEM-EDS element analysis. Fe2O3 and Co3O4 were found to react with YBa2Cu3O7-delta, while ZnO and YBa2Cu3 O7-delta showed no interaction. The phase composition of the product w as found to depend on the concentrations of Fe2O3 and Co3O4 in the rea ction mixture. Reactions with Fe2O3 yielded CuO, tetragonal Fe-doped 1 23-phase and BaCuO2+delta at values of r<0.5. For r=2.0, the 123-phase decomposed and the reaction product contained CuO, YBaCuFeO5+delta an d BaFeO2+delta. Reactions with Co3O4 resulted in Co-doped 123-phase, B aCuO2+delta and CuO, at values of r<1.0. For r=2.0, YBaCuCoO5+delta, B aCoO2+delta and CuO resulted. In addition monophasic YBaCuFeO5+delta ( a=3.8699+/-4 angstrom, c=7.672+/-1 angstrom) and YBaCuCoO5+delta (a=3. 8712+/-2 angstrom, c=7.5658+/-6 angstrom) have been prepared.