Synthesis and physicochemical characterizations of a new valence-mixed pyrophosphate: Cu0.5Zn0.5Fe2(P2O7)2

A new valence-mixed iron(III)-zinc(II)-copper(II) pyrophosphate, Cu2+0.5 Zn2+0.5 Fe3+2 (P2O74−)2, has been synthesized by a dry-way method and structurally characterized by several techniques. The powder diffraction pattern of the new material shows that the pyrophosphate is isostructural with the iron(III)-iron(II) pyrophosphate Fe2+Fe3+2 (P2O74−)2, crystallizing in an orthorhombic arrangement in the Pnma space group. Cu2+Fe3+2 (P2O74−)2 was formed as a secondary phase, as determined both by X-ray diffraction and Mössbauer spectroscopy. Mössbauer spectroscopy and magnetometry measurements showed that Cu0.5Zn0.5Fe2(P2O7)2 is paramagnetic at room temperature and the iron ions are in octahedral coordination. Néel temperature is about 3 K. Infrared and Raman spectroscopies were also used in this study to characterize the new pyrophosphate.