New polymorph of HfMo2O8 synthesized using a high-pressure and high-temperature toroid anvil setup -: art. no. 184106

We report the synthesis and characterization of a new polymorph (beta) of HfMo2O8. This phase is synthesized from the trigonal (alpha) HfMo2O8 by application of high pressures and high temperatures. The sample obtained is characterized by powder x-ray diffraction (XRD) and the details of high-pressure and high-temperature phase are explained. The Rietveld analysis of the powder XRD data reveals that the beta-HfMo2O8 crystallizes in a monoclinic lattice with unit cell parameters a=11.4138(6), b=7.9105(4), c=7.4395(3), A and beta=122.35(0)degrees. The beta-HfMo2O8 is found to be isostructural to the room-temperature phase of beta-ZrMo2O8. The coordination numbers of Hf and Mo atoms with oxygen atoms are eight and five, respectively. The nature and sharing of Hf and Mo polyhedra are entirely different in beta modification compared to that in the alpha phase.