Solid solutions in the Ba₂Y_1-xCu_xWO_6-y system

The crystalline structure of the Ba₂Y_1-xCu_xWO_6-y system was obtained from x-ray diffraction measurements as a function of copper concentration. Five different x regions are observed, four of which correspond to solid solutions and lie at x ≤ 0.75. The crystalline structure of the phases at these copper concentrations has cubic symmetry with lattice parameters between 0.8382 and 0.8275 nm. At 0.75 < x ≤ 1.0 the samples are a mixture of two phases. In this study we have identified the existence of only two stoichiometric compounds: Ba₈Y₃CuW₄O₂₄ with a cubic crystalline structure with space group Pm3m and lattice parameter of 0.8350(1) nm, and Ba₂CuWO₆ with a crystalline tetragonal structure and space group I4/mmm and lattice parameters a = 0.5566(1) nm and c = 0.8634(1) nm. The crystalline structure at all copper concentrations is based in the ordered perovskite structure. The samples show electrical insulator behavior.