Phase equilibria and crystal chemistry of the R–Cu–Ti–O systems (R=lanthanides and Y)

As part of the study of interaction of the Ba2RCu3O6+z (R=lanthanides and Y) superconductor with SrTiO3 buffer, phase equilibria of the subsystem, R2O3–TiO2–CuO (R=Nd, Y, and Yb), have been investigated in air at 960 °C. While the phase relationships of the two phase diagrams with smaller R (Y and Yb) are similar, substantial differences were found in the Nd2O3–TiO2–CuO system, partly due to different phase formation in the binary R2O3–TiO2 and R2O3–CuO systems. R2CuTiO6 and R2Cu9Ti12O36 were the only ternary phases established in all the three diagrams. R2Cu9Ti12O36 belongs to the perovskite-related [AC3](B4)O12 family which is cubic Im3. Depending on the size of R3+, R2CuTiO6 crystallizes in two crystal systems: Pnma (R=La–Gd), and P63cm (R=Dy–Lu). The structure and crystal chemistry of the Pnma series of R2CuTiO6 (R=La, Nd, Sm, Eu, and Gd) are discussed in detail in this paper. Patterns for selected members of R2CuTiO6 have also been prepared and submitted for inclusion in the Powder Diffraction File (PDF).

Grapical abstractPhase diagram of the Y2O3–CuO–TiO2 system prepared in air at 960 °CFigure optionsDownload as PowerPoint slide