Extensive Investigation of High-Pressure Tungsten Dioxide β-WO2

Red single crystals of beta-WO2 were synthesized under high-pressure/high-temperature conditions of 13.1 GPa and 1693 K in a Walker-type multianvil apparatus. beta-WO2 crystallizes in the space group Pnma (Z =12) with the lattice parameters a = 9.7878(5), b =8.4669(4), c=4.7980(2) angstrom, and V= 397.62(3) angstrom(3). The structure consists exclusively of WO6 octahedra, forming a twinned distorted rutile type structure. Temperature dependent X-ray powder diffraction measurements at normal pressure conditions revealed an irreversible phase transition from beta-WO2 to alpha-WO2 between 1173 and 1223 K. Magnetic measurements showed weakly positive susceptibility values which increase to lower temperatures. This is caused by traces of paramagnetic impurities. DFT calculations predict beta-WO2 to be a semiconductor with an indirect band gap of about 0.6 eV.

Automated summary

Red single crystals of beta-WO2 with a distorted rutile type structure consisting of WO6 octahedra were synthesized under high-pressure/high-temperature conditions. A temperature dependent X-ray powder diffraction measurement revealed an irreversible phase transition from beta-WO2 to alpha-WO2. Magnetic measurements showed weakly positive susceptibility values, possibly due to paramagnetic impurities. DFT calculations predicted beta-WO2 to be a semiconductor with an indirect band gap.