Ferroelectric properties and structural refinement of whitlockite-type phosphate Ca8.5Pb0.5Ho(PO4)7. (29th March 2017)

• Record Type: Journal Article
• Authors: Deyneko, Dina V.; Petrova, Darya A.; Leonidova, Olga N.; Nikiforov, Ivan V.; Lazoryak, Bogdan I.
• Is Part Of: Powder diffraction. Volume 32(2017)Supplement 1
• Page Start: S168
• Page End: S171
• Publication Date: 2017-03-29
• Subjects: whitlockite, -- polar structure, -- non-linear optical activity, -- phase transition Rietveld refinement; Powder metallurgy -- Periodicals; Materials -- Analysis -- Periodicals; 620.1127
• DOI: 10.1017/S0885715617000252
• Languages: English
• ISSNs: 0885-7156

Abstract

Abstract : The system of phosphates Ca9− x Pb x Ho(PO4 )7 were obtained by solid-state reaction and were found to be isotypic with whitlockite-type β -Ca3 (PO4 )2 (polar space group R 3 c ). The crystal structure encloses five crystallographic sites M 1– M 5 different in size and oxygen coordination. The unit-cell parameters were determinate using Le Bail decomposition. Rietveld method structural refining showed that Ho 3+ ions are located statistically with calcium in M 1 and M 2 sites, while Pb 2+ -ions are located in the M 3 site. Examination of optical second-harmonic generation evidences non-linear optical activity and confirms polar space group R 3 c . Structural mechanisms and dielectric features of phase transitions are strongly influenced by the exact distributions of atoms over the crystallographic sites.