A site occupancy analysis of zirconolite CaZrxTi3?xO7 |
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| Authors: | R W Cheary A A Coelho |
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| Institution: | Department of Applied Physics, University of Technology, Sydney, Broadway, New South Wales, Australia 2007 Fax: (02)3302219; e-mail: cheary@phys.uts.edu.au, AU
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| Abstract: | The site occupancies of the zirconolite CaZrxTi3?xO7 over its solid solution range from x≈0.8 to x≈1.30 are determined using Rietveld refinement on X-ray powder diffraction data. A phase analysis of the specimens is also incorporated in the refinement to determine the proportions of zirconolite and any impurity phases present namely TiO2, ZrO2 or CaTiO3. Chemical integrity of the refinement is achieved by constraining the total cation content of each specimen to be the same as the pre-fired starting materials weighed out for each specimen. From the results of the quantitative phase analysis and the observed variation of the lattice parameters, it is established that the solid solution range extends from x=0.83(1) to x=1.33(1). The site occupancy results show that from x=0.83 to x=1 the increase in Zr content is accommodated predominantly on the Zr site up to a saturation value of ～95% Zr. From x=1 up to x=1.2 the additional Zr is absorbed into the Ti(1) and Ti(2) sites, but beyond x=1.2 the Ti(3) site also takes on Zr. Each of these changes in occupancy pattern shows up as an inflection in one or more of the monoclinic lattice parameters and it is possible to identify qualitatively the extent to which changes in each site influences the various lattice parameters. |
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