NMR study and electrical properties investigation of Zn2P2O7

Abstract

The α-Zn 2 P 2 O 7 compound was obtained by conventional solid-state reaction. The sample was characterized by X-ray powder diffraction, solid state 31 P NMR MAS, and electrical impedance spectroscopy. The solid state 31 P 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 PO 4 groups in the α-Zn 2 P 2 O 7 form. They are characterized by different chemical shift tensor parameters with the local geometrical features of the tetrahedra. Electrical impedance measurements of β-Zn 2 P 2 O 7 , 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.

Impedance spectroscopy study of Pb2P2O7 compound

“…The electrical characterization of Zn 2 P 2 O 7 has already been studied by our group [18]. As a continuation of that work, synthesis and impedance studies of Pb 2 P 2 O 7 were presented and discussed in this paper.…”

“…The bulk activation energy issued from the impedance (0.66 eV) and the modulus (0.61 eV) spectra are close enough to suggest that the Pb 2+ ion transport is probably due to a hopping mechanism. As in Zn 2 P 2 O 7 [18], the transport properties in this material are probably due to displacements of the divalent cations. In the Pb 2 P 2 O 7 structure, Pb 2+ ions are located between sheets of pyrophosphate groups.…”

Dielectric relaxation and ionic conductivity studies of Ag2ZnP2O7

“…The frequency exponent n values fulfill the equation n ¼ 1 À 6kT =W m characteristic of the correlated barrier hopping (CBH) model where W m is the bending energy defined as the required energy to remove the ion from a site to another. The correlation between the CBH model and the crystallographic results permit us to deduce that the conduction is probably due to the motion of Zn 2+ in the cationic layers and/or a long c direction [8].…”

“…The conductivity of the Zn 2 P 2 O 7 compound is very low (s dc ¼ 2 Â 10 À7 Ω À1 cm À1 at 730 K) [8]. The insertion of the monovalent cation in the parental compound ameliorates considerably the electrical conductivity of the material.…”

Dielectric relaxation and ionic conductivity studies of Na2ZnP2O7

“…The correlation between the CBH model and the crystallographic results permit us to deduce that the conduction is probably due to the motion of Zn 2+ in the cationic layers and/or a long c-direction. This compound showed a very low ionic conductivity, when the σ d.c. = 2 × 10 -7 Ω -1 cm -1 at 730 K (Jarboui et al 2010). Furthermore, we successfully introduced a monovalent cation into the Zn 2 P 2 O 7 compound and we have synthesized the A 2 ZnP 2 O 7 (A = Ag and/or Na) compounds.…”