Synthesis, structure and negative thermal expansion of cubic zrw2−xvxo8−x/2 solid solutions

A novel cubic ZrW2−xVxO8−x/2 solid solution series was found to possess similar negative thermal expansion property like the extensively studied ZrW2O8. A tetragonal hydrate ZrW2−xVxO7−x/2(OH)2(H2O)2 up to x = 0.30 was first prepared through acidic steam hydrothermal synthesis, this precursor dehydrates at moderate temperature and converts to an intermediate orthorhombic phase then transforms to corresponding solid solutions at higher temperature. At room temperature cubic ZrW2−xVxO8−x/2 (x = 0–0.24) has α-ZrW2O8 type and ZrW1.70V0.30O7.85 has β-ZrW2O8 type disordering. X-ray diffraction, neutron diffraction and Raman spectroscopy studies support an average crystal structure model of ZrW2−xVxO8−x/2 as a superposition of respective cubic ZrW2O8 and ZrV2O7 structures. The lattice parameters of cubic ZrW2−xVxO8−x/2 solid solutions, the value of orientation order parameter ω and order–disorder phase transition temperature of the solid solutions all decrease with increasing substitution content x. The maximum solid solubility of cubic ZrW2−xVxO8−x/2 solid solution reaches 16% according to the Vegard’s law.

Cubic ZrW2−xVxO8−x/2 solid solutions whose structure as superposition of cubic ZrW2O8 and ZrV2O7 structures has large solid solubility 16 %.Figure optionsDownload as PowerPoint slideHighlights
► Novel cubic ZrW2−xVxO8−x/2 solid solutions and their precursors were synthesized.
► Cubic ZrW2−xVxO8−x/2 solid solutions show excellent negative thermal expansion.
► Aliovalent substitution of W by V leads to an unusually large solid solubility of 16%.
► Cubic ZrW2−xVxO8−x/2 is a superposition of cubic ZrW2O8 and ZrV2O7 structure.