Abstract
During a study into the synthesis of minerals composed of mining wastes aimed at improving their immobilisation, a cadmium arsenate apatite has been prepared by hydrothermal methods. The structure of this apatite was analysed by single crystal X-ray diffraction, and was found to consist of a standard apatite framework based on Cd-5(AsO4)(3)X, where X represents an anion resident on the (0,0,0.25) site. The framework is hexagonal with the space group P6(3)/m (no 176), a = 9.9709(8), c = 6.4916(4) Angstrom. The X ion site is predominantly occupied by Cl- ions; however due to significant shortening of the c axis exhibited by all cadmium containing apatite phases, a pure chlorapatite is not possible without a significant cation deficiency. No evidence of the necessary deficiency was found in the crystal structure. For larger bromo- and iodo-apatites significant modulations along the c-axis are required to accommodate the halide. This paper examines a number of compensation mechanisms and proposes that a minor disorder of chloride, oxide and hydroxide located on the X ion site provides the required charge compensation mechanism. This is contrary to previous complex modulations proposed in the literature. The proposed chemical formula is Cd-5(AsO4)(3)Cl(1-2x-y)O(x)square(x)OH(y) where square represents a vacancy.
Original language | English |
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Pages (from-to) | 3611-3615 |
Number of pages | 4 |
Journal | Dalton Transactions |
Issue number | 21 |
DOIs | |
Publication status | Published - 2004 |
Keywords
- CD5(PO4)3CL
- database