Conditions for the formation of a non-autonomous phase at the structural deformation of complex vanadium oxides

Received: 02.03.2018. Accepted: 10.04.2018. Published: 10.05.2018.A new previously unknown effect of a reversible transition from a singlephase system to a heterophase system containing a non-autonomous phase was observed during thermal and chemical deformations of the Zn2–2xCd2xV2O7 structure.The role of local symmetry in the formation of the non-autonomous phase is shown on the basis of X-ray diffraction studies in situ and a comparative crystal-chemical analysis of the structural deformations of isoform monoclinic solid solutions of zinc and copper pyrovanadates with zero volumetric thermal expansion.The work was supported by UB RAS (project 18-10-3-32)

Sol-gel synthesis and crystal chemical properties of the pigment Zn1.9Cu0.1SiO4

Received: 06.12.2018. Accepted: 21.12.2018. Published: 31.12.2018.The pigment Zn1.9Cu0.1SiO4 was obtained by the method of sol-gel synthesis. The crystallization temperature was set at 776 °C, ΔH ≈ –16.3 kJ / mol. Thermal expansion of the individual Zn2SiO4 and Zn1.9Cu0.1SiO4 solid solutions was studied by in situ high-temperature X-ray diffraction. It is shown that the substitution of Zn2+ → Cu2+ does not lead to significant changes in the lattice parameters; in the range from room temperature to 800 °C the structure expands monotonically when heated. The coefficients of volumetric thermal expansion for Zn2SiO4 and Zn1.9Cu0.1SiO4 are αV = 8.05 · 10–6 and 8.81 · 10–6 1 / K, respectively. The colorimetric coordinates in the RGB system are 71.8 % red, 72.9 % green and 79.6 % blue, which corresponds to the gray-blue pigment.The work was supported by UB RAS (project 18‑10‑3‑32)