Crystal Chemistry of Cd2-xCaxP2O7, 0 ≤ x ≤ 2 and the Structure Analysis of Cd1.25Ca0.75P2O7
1993; Elsevier BV; Volume: 106; Issue: 2 Linguagem: Inglês
10.1006/jssc.1993.1311
ISSN1095-726X
AutoresA. Alaoui El Belghiti, Ali Boukhari, Elizabeth M. Holt,
Tópico(s)Crystal Structures and Properties
ResumoThe system, Cd2-xCaxP2O7, 0 ≤ x ≤ 2, has been prepared in powder form at 1173 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 Cd1.25Ca0.75P2O7(Cd2-xCaxP2O7, x = 0.75) has been isolated in domain B (0.4 ≤ x ≤ 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), b = 7.222(2), c = 6.667(2) Å, α = 122.93(2), β = 154.78(9), γ = 60.68(2)°, and Z = 2. A final least squares refinement yielded R = 5.4% for 1531 observed reflections. The solid state structure is of the dichromate family, containing isolated and eclipsed P2O4-7 groups which form columns parallel to the c axis of the triclinic cell. A Cd2+ ion with sixfold coordination to oxygen [Cd-O av. 2.30(3) Å] and a mixed Cd2+/Ca2+ site [eightfold oxygen coordination, M -O, 2.54(4) Å] are located between these columns.
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