Institution: | a Department of Chemistry, Faculty of Science, Moulay Ismaïl University, Meknes, Morocco b Institut de Chimie de la Matiére Condensée de Bordeaux CNRS, Chateau Brivazac, F-33600, Pessac, France |
Abstract: | A 19F-NMR investigation of the Pb1 − xAlxF2 + x (0 ≤ x ≤ 0.12) solid solution and of the ordered Pb9Al2F24 phase is undertaken as a function of temperature. Several F− ion groups become progressively mobile at the NMR time scale at increasing temperature, the first, (Fi)pb and (Fn)pb, are located in the surroundings of Pb2+ cations, the second ones, (Frd)AI and (Fra)Al, in that of Al3+ cations. Four types of fluoride ions are distinguished in the 19F-NMR spectra of rigid lattice at low temperature (T = 175 K) and the distribution of fluoride ions among the four sites is determined by deconvolution of the spectra registered. The sites occupied by the (Fn)pb anions are identified with the normal anionic sites of the fluorite network, the others with different interstitial sites. |