Structural characterization and colour of Mg(x)Cu(3-x)V(2)O(8) (0 ≤ x ≤ 3) and Mg(y)Cu(2-y)V(2)O(7) (0 ≤ y ≤ 2) compositions

In this study, Mg(x)Cu(3-x)V(2)O(8) (0 ≤ x ≤ 3) and Mg(y)Cu(2-y)V(2)O(7) (0 ≤ y ≤ 2) compositions were synthesized by the chemical coprecipitation method and characterized by X-ray diffraction, UV–vis-NIR spectroscopy and CIE L* a* b* parameters measurements. Melting points of compounds Cu(3)V(2)O(8) and Cu(2)V(2)O(7) are 780°C and 790°C, respectively. The addition of small amounts of Mg (II), Mg(x)Cu(3-x)V(2)O(8) (x < 1.0) and Mg(y)Cu(2-y)V(2)O(7) (y < 0.5) fused compositions, was not sufficient to stabilize structures at 800°C. For the Mg(2)CuV(2)O(8) (x = 2.0) composition fired at 800°C, Mg (II) incorporated into the monoclinic Cu(3)V(2)O(8) structure stabilizes this crystalline phase. At 1000°C, orthorhombic Mg(3)V(2)O(8) structure from this composition was obtained. Solid solutions with orthorhombic symmetry were detected from the prepared compositions fired at 1000°C when 1.0 ≤ x ≤ 3.0. The difference of coloration of Cu, Mg vanadates might be explained by the presence of a strong charge transfer band in visible spectra. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s40064-015-0908-8) contains supplementary material, which is available to authorized users.