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Crystal chemistry and the role of ionic radius in rare earth tetrasilicates: Ba 2 RE 2 Si 4 O 12 F 2 (RE = Er 3+ –Lu 3+ ) and Ba 2 RE 2 Si 4 O 13 (RE = La 3+ –Ho 3+ )
Author(s) -
Fulle Kyle,
Sanjeewa Liurukara D.,
McMillen Colin D.,
Kolis Joseph W.
Publication year - 2017
Publication title -
acta crystallographica section b
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.604
H-Index - 33
ISSN - 2052-5206
DOI - 10.1107/s2052520617009544
Subject(s) - ionic radius , crystallography , crystal chemistry , rare earth , ionic bonding , hydrothermal circulation , silicate , chemistry , crystal structure , hydrothermal synthesis , ion , mineralogy , geology , seismology , organic chemistry
Structural variations across a series of barium rare earth (RE) tetrasilicates are studied. Two different formulas are observed, namely those of a new cyclo‐silicate fluoride, BaRE 2 Si 4 O 12 F 2 (RE = Er 3+ –Lu 3+ ) and new compounds in the Ba 2 RE 2 Si 4 O 13 (RE = La 3+ –Ho 3+ ) family, covering the whole range of ionic radii for the rare earth ions. The Ba 2 RE 2 Si 4 O 13 series is further subdivided into two polymorphs, also showing a dependence on rare earth ionic radius (space group for La 3+ –Nd 3+ , and space group C 2/ c for Sm 3+ –Ho 3+ ). Two of the structure types identified are based on dinuclear rare earth units that differ in their crystal chemistries, particularly with respect to the role of fluorine as a structural director. The broad study of rare earth ions provides greater insight into understanding structural variations within silicate frameworks and the nature of f ‐block incorporation in oxyanion frameworks. The single crystals are grown from high‐temperature ( ca 953 K) hydrothermal fluids, demonstrating the versatility of the technique to access new phases containing recalcitrant rare earth oxides, enabling the study of structural trends.