| Autor: |
Dabić P; University of Belgrade, Faculty of Mining and Geology, Đušina 7, Belgrade 11000, Serbia., Nikolić MG; University of Belgrade, Institute of Physics, Pregrevica 118, Belgrade 11080, Serbia., Kovač S; University of Belgrade, Faculty of Mining and Geology, Đušina 7, Belgrade 11000, Serbia., Kremenović A; University of Belgrade, Faculty of Mining and Geology, Đušina 7, Belgrade 11000, Serbia. |
| Jazyk: |
angličtina |
| Zdroj: |
Acta crystallographica. Section C, Structural chemistry [Acta Crystallogr C Struct Chem] 2019 Oct 01; Vol. 75 (Pt 10), pp. 1417-1423. Date of Electronic Publication: 2019 Sep 25. |
| DOI: |
10.1107/S2053229619011926 |
| Abstrakt: |
Two polymorphs of tripotassium erbium disilicate, K 3 ErSi 2 O 7 , were synthesized by high-temperature flux crystal growth during the exploration of the flux technique for growing new alkali rare-earth elements (REE) containing silicates. Their crystal structures were determined by single-crystal X-ray diffraction analysis. One of them (denoted 1) crystallizes in the space group P6 3 /mmc and is isostructural with disilicates K 3 LuSi 2 O 7 , K 3 ScSi 2 O 7 and K 3 YSi 2 O 7 , while the other (denoted 2) crystallizes in the space group P6 3 /mcm and is isostructural with disilicates K 3 NdSi 2 O 7 , K 3 REESi 2 O 7 (REE = Gd-Yb), K 3 YSi 2 O 7 , K 3 (Y 0.9 Dy 0.1 )Si 2 O 7 and K 3 SmSi 2 O 7 . In the crystal structure of polymorph 1, the Er cations are in an almost perfect octahedral coordination, while in the crystal structure of polymorph 2, part of the Er cations are in a slightly distorted octahedral coordination and the other part are in an ideal trigonal prismatic coordination environment. Sharing six corners, disilicate Si 2 O 7 groups in the crystal structure of polymorph 1 link six ErO 6 octahedra, forming a three-dimensional network and nine-coordinated potassium cations are located in its holes. In the crystal structure of polymorph 2, the disilicate Si 2 O 7 groups connect four ErO 6 octahedra, as well as one ErO 6 trigonal prism. Three differently coordinated potassium cations are situated between them. Different site symmetries of the erbium cations in the crystal structures of polymorphs 1 and 2 affect their photoluminescence properties. Only polymorph 2 exhibits luminescence. Intense narrow lines in the emission spectrum are a result of the 4f-4f transition. The green emission line at 560 nm is the result of the Er 3+ transition 4 S 3/2 → 4 I 15/2 , and the luminescence line at 690 nm is the result of a 4 F 9/2 → 4 I 15/2 transition. The crystal morphologies of the two polymorphs are similar. Crystals of polymorph 1 are in the form of a hexagonal prism in combination with a hexagonal base, while crystals of polymorph 2 contain a dihexagonal prism in combination with a hexagonal base, although poorly developed faces of the dihexagonal pyramid can also be noticed. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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