The crystal structure of Ca7Zr7Ta6O36 refined using synchrotron-radiation data.
Single-crystal X-ray diffraction data [synchrotron radiation; lambda = 1.2682 (4) Å] are used to solve and refine the crystal structure of heptacalcium hexatantalum heptazirconium hexatriacontaoxide, Ca(7)Zr(7)Ta(6)O(36). The structure adopts space group Fddd with cell dimensions a = 36.394 (1), b = 7.3674 (5), c = 31.006 (2) Å. The structure was solved by direct methods. Refinement using 1299 unique reflections leads to final values of R = 0.031 and wR = 0.034. The refined metal-atom ordering scheme is far from fully ordered and reminiscent of the A/B metal-atom ordering characteristic of the pyrochlore structure type. Bond-valence sums are calculated to confirm the plausibility of the crystal chemistry of Ca(7)Zr(7)Ta(6)O(36).
Research School of Chemistry, Australian National University, GPO Box 414, Canberra, ACT 2601, Australia. schmid@rsc.anu.edu.au
S
Schmid
JG
Thompson
RL
Withers
CD
Ling
N
Ishizawa
S
Kishimoto