Crystal Chemistry of Cd2-xCaxP2O7, 0 ≤ x ≤ 2 and the Structure Analysis of Cd1.25Ca0.75P2O7

✍ Scribed by A.Alaoui El Belghiti; Ali Boukhari; Elizabeth M. Holt

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 195 KB
• Volume: 106
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1993.1311

✦ Synopsis

The system, (\mathrm{Cd}{2-x} \mathrm{Ca}{x} \mathrm{P}{2} \mathrm{O}{7}, 0 \leq x \leq 2), has been prepared in powder form at (1173 \mathrm{~K}) and found to exist in four domains, A, B, C, and D. The materials of these domains have been identified by powder diffraction methods. A crystal of (\mathrm{Cd}{1.25} \mathrm{Ca}{0.73} \mathrm{P}{2} \mathrm{O}{7}\left(\mathrm{Cd}{2-1} \mathrm{Ca}{x} \mathrm{P}{2} \mathrm{O}{7}, x=0.75\right)) has been isolated in domain B ((0.4 \leq x \leq 1.00)) which has not been previously identified and structurally determined by single crystal X-ray diffraction. This phase crystallizes in the triclinic space group (P 1) bar with (a=15.477(5)), (h=7.222(2), c=6.667(2) \AA, \alpha=122.93(2), \beta=154.78(9), \gamma=60.68(2)^{\circ}), and (Z=2). A finat least squares refinement yielded (R=5.4 %) for 1531 observed reflections. The solid state structure is of the dichromate family, containing isolated and eclipsed (\mathrm{P}{2} \mathrm{O}{7}^{4-}) groups which form columns parallel to the (c) axis of the triclinic cell. (\mathrm{A} \mathrm{Cd}^{2+}) ion with sixfold coordination to oxygen [Cd-O av. 2.30(3) (\AA) ] and a mixed (\mathrm{Cd}^{2+} / \mathrm{Ca}^{2+}) site leightfold oxygen coordination, (M-0,2.54(4) \AA) ] are located between these columns. O 1993 Academic Press, Inc.