Interfacial reactions of Ba2YCu3O6+z with coated conductor buffer layer, LaMnO3

Chemical interactions between the Ba2YCu3O6+x superconductor and the LaMnO3 buffer layers employed in coated conductors have been investigated experimentally by determining the phases formed in the Ba2YCu3O6+x-LaMnO3 system. The Ba2YCu3O6+x-LaMnO3 join within the BaO-(Y2O3-La2O3)-MnO2-CuOx multi-component system is non-binary. At 810 °C (pO2 = 100 Pa) and at 950 °C in purified air, four phases are consistently present along the join, namely, Ba2−x(La1+x−yYy)Cu3O6+z, Ba(Y2−xLax)CuO5, (La1−xYx)MnO3, (La,Y)Mn2O5. The crystal chemistry and crystallography of Ba(Y2−xLax)CuO5 and (La1−xYx)Mn2O5 were studied using the X-ray Rietveld refinement technique. The Y-rich and La-rich solid solution limits for Ba(Y2−xLax)CuO5 are Ba(Y1.8La0.2)CuO5 and Ba(Y0.1La1.9)CuO5, respectively. The structure of Ba(Y1.8La0.2)CuO5 is Pnma (No. 62), a = 12.2161(5) Å, b = 5.6690(2) Å, c = 7.1468(3) Å, V = 494.94(4) Å3, and Dx = 6.29 g cm−3. YMn2O5 and LaMn2O5 do not form solid solution at 810 °C (pO2 = 100 Pa) or at 950 °C (in air). The structure of YMn2O5 was confirmed to be Pbam (No. 55), a = 7.27832(14) Å, b = 8.46707(14) Å, c = 5.66495(10) Å, and V = 349.108(14) Å3. A reference X-ray pattern was prepared for YMn2O5.