Evidence of a new bismuth vanadium zinc oxyfluoride with the BIMEVOX structure

Substitution of oxygen by fluorine in a bismuth vanadium zinc oxide belonging to the BIMEVOX family has allowed the synthesis of a mixed anion (O, F) phase which can be considered as the first member of a new BIIMEVOF family. As for the corresponding BIZNVOX phase, three different forms (alpha, beta and gamma) have been identified, depending upon the composition and the temperature. The high temperature gamma form can be stabilized down to room temperature for a lower Zn content than in the oxide derivatives. X-ray diffraction, thermal analysis and density measurements have been used to confirm that fluorine partly substitutes oxygen leading to the formation of the solid solution: Bi(2)V(1-x-y)Zn(x)Bi(y)O(5.5-2.5x-y)F(2x). The evolution of electrical conductivity with fluorine ratio has been investigated by impedance spectroscopy. (C) 1998 Elsevier Science B.V. All rights reserved.