NMR study and electrical properties investigation of Zn2P2O7

The alpha-Zn2P2O7 compound was obtained by conventional solid-state reaction. The sample was characterized by X-ray powder diffraction, solid state P-31 NMR MAS, and electrical impedance spectroscopy. The solid state P-31 MAS NMR, performed at 121.49 MHz, shows three isotropic resonances at -21.1, -18.8, and -15.8 ppm, confirming the non-equivalency of the three PO4 groups in the alpha-Zn2P2O7 form. They are characterized by different chemical shift tensor parameters with the local geometrical features of the tetrahedra. Electrical impedance measurements of beta-Zn2P2O7, form stable for temperature greater than 403 K, were performed as a function of both temperature and frequency. The electrical conduction and dielectric relaxation have been studied. The AC conductivity obeys the universal power law. The approximation type correlated barrier hopping model explains the universal behavior of the n exponent. The impedance plane plot shows semicircle arcs at different temperatures, and an electrical equivalent circuit has been proposed to explain the impedance results. The circuits consist of the parallel combination of bulk resistance R (p) and constant phase elements CPE. The simulated spectra show a good correlation with the experimental data.