High-temperature behavior of vanadyl pyrophosphate (VO)₂P₂O₇

Titelangaben

van Smaalen, Sander ; Dinnebier, Robert E. ; Hanson, Jonathan ; Gollwitzer, Jan ; Büllesfeld, Frank ; Prokofiev, Andrei ; Assmus, Wolf:
High-temperature behavior of vanadyl pyrophosphate (VO)₂P₂O₇.
In: Journal of Solid State Chemistry. Bd. 178 (2005) Heft 7 . - S. 2225-2230.
ISSN 0022-4596
DOI: https://doi.org/10.1016/j.jssc.2005.04.034

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Abstract

(VO)2P2O7(VO)2P2O7 has been studied at high temperatures by in situ X-ray powder diffraction in an inert atmosphere. Lattice parameters indicate an anisotropic thermal expansion up to View the MathML sourceTc=214∘C, followed by an approximately isotropic expansion up to View the MathML source490∘C. It is proposed that TcTc is the temperature of a second-order phase transition between the known room temperature form with space group Pca21Pca21 and a high-temperature form with space group Pcab . Above View the MathML source490∘C a minority phase develops in the sample that was identified as the V3+V3+ containing compound V4(P2O7)3V4(P2O7)3, while the anisotropic expansion along aa suggests that stoichiometric (VO)2P2O7(VO)2P2O7 transforms into (VO)2P2O7+x(VO)2P2O7+x with interstitial oxygen located between the layers. With an onset at View the MathML source706∘C all of the (VO)2P2O7(VO)2P2O7 transforms into VPO4VPO4.