Synthesis and crystal structure of Mg1-xCu2+xO3 (0.130 <= x <= 0.166)

Solid solutions of Mg1-xCu2+xO3 were prepared at 950 degreesC for 12 h in a ir with a narrow composition range of x from 0.130 to 0.166. Thermal analys is revealed that the sample of x = 0.143 decomposed into MgO and Cu2O above 1030 degreesC. The stoichiometric oxygen content based on Cu II valence wa s confirmed with the weight loss after decomposition in H-2:Ar (20%:80%) at mosphere. The X-ray powder diffraction pattern of the sample (x = 0.143) wa s analyzed by the Rietveld method. The structure is isostructural with CaCu 2O3, and related to a rock-salt-type superstructure with an orthorhombic ce ll, a = 3.9906(1), b = 9.3482(3), and c = 3.1911 (1) Angstrom, space group Pmmn (No. 59, setting 2). There are two metal atom sites in the structure. One metal atom site (4e) occupied by Cu atoms is in an elongated octahedron of oxygen atoms. The other site (2b) is statistically occupied by Cu and M g atoms with fractions of 0.143 and 0.857, respectively. (C) 2001 Academic Press.