Crystal structure and thermal expansion studies of α-VO(PO3)2

In this manuscript the details of the crystal structure and thermal expansion characteristics of the α-VO(PO3)2 are being discussed. Pale blue-colored sample of VO(PO3)2 has been prepared by solid-state reaction of V2O5 and (NH4)2HPO4 at elevated temperature and analyzed by the Rietveld refinement of the observed ambient temperature powder X-ray diffraction (XRD) data for the phase purity and crystal structure. The observed unit cell parameters for α-VO(PO3)2 at ambient temperature are: a = 15.0924(4), b = 4.1919(1), c = 9.5706(3) Å, β = 126.464(2)° and V = 486.95(3) Å3, Z = 4 (space group: C2/c, no. 15). In the temperature range of 25–900 °C, the high-temperature behavior of this compound has been studied by an in situ high-temperature X-ray diffraction (HTXRD). This compound shows a significantly higher thermal expansion with the increase in temperature. The observed unit cell parameters at 900 °C are: a = 15.508(1), b = 4.3527(3), c = 9.8234(9) Å, β = 127.759(6)°, V = 524.26(7) Å3. The typical thermal expansion coefficient of unit cell volume (αv) is 89.2 × 10−6 °C−1. The further details of the high-temperature behaviors are explained in this manuscript.