Thermal Behavior of Zinc Phenylphosphonate and Structure Determination ofγ-Zn2P2O7from X-Ray Powder Diffraction Data

Abstract

The thermal behavior of zinc phenylphosphonate has been studied by temperature-dependent X-ray powder diffraction and thermo-gravimetry in the temperature range 19–600°C. The different phases occurring during the decomposition have been identified, i.e., the anhydrous phase and the three successive polymorphic varieties of Zn2P2O7. The first one is amorphous,δ-Zn2P2O7is poorly crystalline, andγ-Zn2P2O7is a metastable phase. The last transforms into theβvariety at higher temperature. The crystal structure ofγ-Zn2P2O7has been solvedab initiofrom powder diffraction data collected with conventional monochromatic X-rays. The symmetry is orthorhombic with the cell dimensionsa=4.9504(5) Å,b=13.335(2) Å,c=16.482(3) Å, space groupPbcm,Z=8. The structure consists of infinite corrugated chains of ZnO5trigonal bipyramids, running along [001]. These chains are linked together by P2O7groups in the two other directions. The P2O4−7anions display low angles and an eclipsed conformation, contrary to theαandβphases.