Abstract
The structure of Ca8.4Bi1.6(PO4)(6)O-1.8, isostructural with Fluoroapatite, was determined by X-ray powder diffraction methods. The results of Rietveld refinement revealed that the formula of this compound is [Ca-4](4h)[Ca4.4Bi1.6](6h)(PO4)(6)[O-1.8](2a), space group P63/m (a=9.468 (3)angstrom, c=6.957 (3)angstrom). A total substituition of Bi3+ ions in the (6h) sites was related particularly to the high polarizability of the Bi3+ ion compared to Ca2+.
The observed frequencies in the Raman and infrared spectra were explained and discussed on the basis of unit-cell group analyses and in comparison with Fluoroapatite and other oxyapatites. The ionic conductivity over a wide range of temperature was investigated according to the complex impedance method. The highest overall conductivity values were found at sigma(700) degrees C = 5.03 x 10(-7) S cm(-1) and E-a=0.50 eV. (C) 2012 Elsevier Inc. All rights reserved.