Variation of cation distribution with temperature and its consequences on thermal expansion for Ca3Eu2(BO3)4. Issue 4 (13th July 2020)

• Record Type: Journal Article
• Authors: Kosyl, Katarzyna M.; Paszkowicz, Wojciech; Shekhovtsov, Alexey N.; Kosmyna, Miron B.; Antonowicz, Jerzy; Olczak, Adam; Fitch, Andrew N.
• Is Part Of: Acta crystallographica. Volume 76:Issue 4(2020:Aug.)
• Page Start: 554
• Page End: 562
• Publication Date: 2020-07-13
• Subjects: calcium borates -- rare earths -- thermal expansion anisotropy -- site occupation -- disordered structure
• DOI: 10.1107/S2052520620006757
• Languages: English
• ISSNs: 2052-5206

Abstract

Abstract : The structural behavior of Ca3 Eu2 (BO3 )4 at high temperature was investigated. A change in thermal expansion anisotropy was found at around 923 K, connected to a variation of Ca/Eu distribution over the three cationic sites. Abstract : The structure of calcium europium orthoborate, Ca3 Eu2 (BO3 )4, was determined using high‐resolution powder X‐ray diffraction data collected at the ID22 beamline (ESRF) under ambient conditions, as well as at high temperature. Rietveld refinement allowed determination of the lattice constants and structural details, including the Ca/Eu ratios at the three cationic sites and their evolution with temperature. Clear thermal expansion anisotropy was found, and slope changes of lattice‐constant dependencies on temperature were observed at 923 K. Above this temperature the changes in occupation of the Ca/Eu sites occur, exhibiting a tendency towards a more uniform Eu distribution over the three Ca/Eu sites. Possible structural origins of the observed thermal expansion anisotropy are discussed.