Single crystal growth of Zn_xCu_1–x V₂O₇ (x = 0.05, 0.15) by the vertical gradient freezing technique

Single crystals of Zn_xCu_1−xV₂O₇ system with doping concentration of x = 0.05 and 0.15 were grown by the vertical gradient freezing technique. The crystal structures were confirmed by means of x-ray diffraction to be the beta phase of copper pyrovanadate, β-Cu₂V₂O₇, when the Zn concentration was as low as 0.05, on the contrary to the previous studies on polycrystal samples. The Rietveld refinements on x-ray diffraction patterns showed that that lattice constants were slightly increased, whereas the angle β was slightly decreased, when the doping concentration was decreased from x = 0.15 to 0.05. θ-2θ scan confirmed that the natural cleaved facet is crystallographic a-axis with FWHM around (200) peak of lower than 0.2°, suggesting a high quality of the obtained single crystals. (paper)