Study of the crystal structures of new buffer materials Bi _1-x y _x O _1.5

Bismuth based oxides, formed by bismuth oxide doped with the yttrium or lanthanum element, have been widely studied for their high ionic conductivities and other applicable properties. Recently, they were used as buffer layers for film superconductors and have shown a promising future. But the detailed information of their structures and properties has not been fully understood. In this work, the series samples of Bi _1-x Y _x O _1.5 (x=0.2, 0.3, 0.4, and 0.5, respectively) were prepared. The crystalline structures of them were determined by X-ray powder diffraction and the data were analyzed by Rietveld refinement method. Two phases, face centered cubic (FCC) and rhombohedral structures, were observed. When annealed at 1,000∈°C, the samples are FCC structure. But for Bi _0.8Y _0.2O _1.5, annealed at 650∈°C, the sample shows a rhombohedral structure. The change of the structures of the samples were studied and discussed.