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Ferroelectric properties and structural refinement of whitlockite-type phosphate Ca8.5Pb0.5Ho(PO4)7
Published online by Cambridge University Press: 29 March 2017
Abstract
The system of phosphates Ca9−xPbxHo(PO4)7 were obtained by solid-state reaction and were found to be isotypic with whitlockite-type β-Ca3(PO4)2 (polar space group R3c). The crystal structure encloses five crystallographic sites M1–M5 different in size and oxygen coordination. The unit-cell parameters were determinate using Le Bail decomposition. Rietveld method structural refining showed that Ho3+ ions are located statistically with calcium in M1 and M2 sites, while Pb2+-ions are located in the M3 site. Examination of optical second-harmonic generation evidences non-linear optical activity and confirms polar space group R3c. Structural mechanisms and dielectric features of phase transitions are strongly influenced by the exact distributions of atoms over the crystallographic sites.
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- Copyright © International Centre for Diffraction Data 2017
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