Crystal structure and phase transitions of strontium zirconium diorthophosphate, SrZr(PO4)2 |
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Authors: | Koichiro Fukuda Akira Moriyama Shinobu Hashimoto |
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Affiliation: | Department of Environmental and Materials Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya-shi, Aichi-ken 466-8555, Japan |
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Abstract: | The crystal structure of SrZr(PO4)2 at 298 K was determined from conventional X-ray powder diffraction data using direct methods, and it was further refined by the Rietveld method. The structure was triclinic (space group , Z=2) with a=0.77508(4) nm, b=0.78887(5) nm, c=0.51251(3) nm, α=95.754(3)°, β=90.228(2)°, γ=92.474(2)°, and V=0.31149(3) nm3. Final reliability indices were Rwp=8.51%, Rp=6.07%, and RB=2.46%. The powder specimens were also examined by high-temperature XRD and differential thermal analysis to reveal the occurrence of phase transitions from triclinic to monoclinic at 405 K, then to hexagonal (or trigonal) at 1196 K during heating. Upon cooling, the reverse change of the latter transition occurred at 1175 K. The subsequent monoclinic-to-triclinic transition was martensitic and incomplete during further cooling to 298 K. The monoclinic phase is most probably isostructural with yavapaiite. The present paper has described, for the first time, the higher- and lower-temperature polymorphs of the yavapaiite-type structure. |
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Keywords: | Strontium zirconium diorthophosphate Phase transitions High-temperature XRD Rietveld method |
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