Solid State Ionics, Vol.150, No.3-4, 431-442, 2002
Structural modifications of dodecatungstophosphoric acid hexahydrate induced by temperature in the 10-358 K range. In situ high-resolution neutron powder diffraction investigation
Dodecatungstophosphoric acid hexahydrate H3PW12O40.6H(2)O crystal structure has been investigated by neutron powder diffraction (NPD) at different temperatures in the 10-358 K range. A nonconvergent reversible phase transition has been noticed at about 320 K. This transition is associated with a change in dynamic equilibrium of hydrate species and partial reduction/oxidation (redox) W6+<---->(5+). Expressive structure changes lie in the P-O bonding inside Keggin's anion and the H5O2+ conformational angle.
Keywords:crystal structure;dodecatungstophosphoric acid hexahydrate;neutron powder diffraction;nonconvergent phase transition;dioxonium ion;disorder