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J. Phys. IV France
Volume 113, January 2004
Page(s) 115 - 118

J. Phys. IV France
113 (2004) 115
DOI: 10.1051/jp4:20040025

Étude des propriétés de conduction électrique des phosphates condensés mixtes éléments monovalents-terres rares : LiDy(PO 3) 4, NaNd(PO 3) 4, AgLa(PO 3) 4, NH 4DyPO 3) 4

M. Férid1, K. Horchani1, A. Touai2, A. Madani2, H. Boussetta2 and M. Trabetsi-Ayedi3

1  Laboratoire des Procédés Chimiques, Institut National de Recherche Scientifique et Technique, BP. 95, 2050 Hammam-Lif, Tunisie
2  Laboratoire de Physique des Matériaux, Faculté des Sciences de Bizerte, 7021 Zarzouna, Tunisie
3  Laboratoire de Physique-Chimie Minérale, Faculté des Sciences de Bizerte, 7021 Zarzouna, Tunisie

Single crystals of LiDy(PO 3) 4, NaNd(PO 3) 4, NH 4Dy(PO 3) 4 and AgLa(PO 3) 4 polyphosphates have been grown using the flux method. A mixture of monovalent carbonate (M 2CO 3), rare earth oxide (Ln 2O 3) and phosphoric acid (H 3PO 4 85%) was heated at 285°C during a week. Single crystals were obtained and characterized by X-ray diffraction, infrared and Raman spectroscopy. Their investigation was carried out by thermal analysis (ATG/ATD). Their electric conductivity was measured by impedance spectroscopy. The conductivity, $\sigma$, vary between $1{,}5\times10^{-8}~\Omega^{-1}$.cm -1 at 300 °C and $2\times10^{-5}~\Omega^{-1}$.cm -1 at 500 °C. The activation energies increase from 0,31 for NH 4Dy(PO 3) 4 to 1,26 eV for NaNd(PO 3) 4. The basic structural units of these phosphates are ribbons (PO 3) $_{\rm n}$ formed by corner-sharing of PO 4 tetrahedra with variable geometry, which are unfavourable to the ionic conduction. The ionic transport was mainly assured by M + ions; moreover, the hydrogen bond established in the structure of NH 4Dy(PO 3) 4 and the proton exchange allow to explain the relatively high conductivity of this phosphate. The results are discussed and correlated to the structural properties of these phosphates.

© EDP Sciences 2004