Rietveld study of the structural phase transition in the sanmartinite (ZnWO4)-cuproscheelite (CuWO4) solid solution
Redfern, Simon A. T.; Bell, Anthony M. T.; Henderson, C. Michael B.; Schofield, Paule
European Journal of Mineralogy Volume 7 Number 4 (1995), p. 1019 - 1028
published: Aug 1, 1995
manuscript accepted: Mar 8, 1995
manuscript received: Sep 24, 1994
ArtNo. ESP147050704025, Price: 29.00 €
Abstract The P1̄ to Pile phase transition in Cu1-xZnxWO4 has been investigated by observing structural changes across the solid solution. The crystal structures of samples with x = 0.85, 0.55 and 0.30 have been refined by the Rietveld method from high-resolution synchrotron X-ray diffraction data. The Cu/Zn and W atoms are in distorted octahedral coordination. The microscopic order parameter (defined in terms of changes in Cu/Zn-O bond lengths) behaves in a similar manner to the previously-recorded macroscopic spontaneous strain. Rigid-unit-mode analysis shows that the transition does not involve distortions of a framework of rigid octahedra. Rather, the co-operative Jahn-Teller distortion of the CuO6 octahedra is identified as the driving mechanism, with WO6 octahedral distortions occurring as a secondary process.