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Author |
Morozov, V.A.; Arakcheeva, A.V.; Pattison, P.; Meert, K.W.; Smet, P.F.; Poelman, D.; Gauquelin, N.; Verbeeck, J.; Abakumov, A.M.; Hadermann, J. |
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Title |
KEu(MoO4)2 : polymorphism, structures, and luminescent properties |
Type |
A1 Journal article |
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Year  |
2015 |
Publication |
Chemistry of materials |
Abbreviated Journal |
Chem Mater |
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Volume |
27 |
Issue |
27 |
Pages |
5519-5530 |
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Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
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Abstract |
In this paper, with the example of two different polymorphs of KEu(MoO4)2, the influence of the ordering of the A-cations on the luminescent properties in scheelite related compounds (A′,A″)n[(B′,B″)O4]m is investigated. The polymorphs were synthesized using a solid state method. The study confirmed the existence of only two polymorphic forms at annealing temperature range 9231203 K and ambient pressure: a low temperature anorthic α-phase and a monoclinic high temperature β-phase with an incommensurately modulated structure. The structures of both polymorphs were solved using transmission electron microscopy and refined from synchrotron powder X-ray diffraction data. The monoclinic β-KEu(MoO4)2 has a (3+1)-dimensional incommensurately modulated structure (superspace group I2/b(αβ0)00, a = 5.52645(4) Å, b = 5.28277(4) Å, c = 11.73797(8) Å, γ = 91.2189(4)o, q = 0.56821(2)a*0.12388(3)b*), whereas the anorthic α-phase is (3+1)-dimensional commensurately modulated (superspace group I1̅(αβγ)0, a = 5.58727(22) Å, b = 5.29188(18)Å, c = 11.7120(4) Å, α = 90.485(3)o, β = 88.074(3)o, γ = 91.0270(23)o, q = 1/2a* + 1/2c*). In both cases the modulation arises due to Eu/K cation ordering at the A site: the formation of a 2-dimensional Eu3+ network is characteristic for the α-phase, while a 3-dimensional Eu3+-framework is observed for the β-phase structure. The luminescent properties of KEu(MoO4)2 samples prepared under different annealing conditions were measured, and the relation between their optical properties and their structures is discussed. |
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Wos |
000360323700011 |
Publication Date |
2015-07-29 |
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ISSN |
0897-4756;1520-5002; |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
9.466 |
Times cited |
26 |
Open Access |
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Notes |
278510 Vortex; Fwo G039211n; G004413n ECASJO_; |
Approved |
Most recent IF: 9.466; 2015 IF: 8.354 |
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Call Number |
c:irua:127244 |
Serial |
3537 |
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Author |
Morozov, V.A.; Arakcheeva, A.V.; Konovalova, V.V.; Pattison, P.; Chapuis, G.; Lebedev, O.I.; Fomichev, V.V.; Van Tendeloo, G. |
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Title |
LiZnNb4O11.5 : a novel oxygen deficient compound in the Nb-rich part of the Li2O-ZnO-Nb2O5 system |
Type |
A1 Journal article |
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Year |
2010 |
Publication |
Journal of solid state chemistry |
Abbreviated Journal |
J Solid State Chem |
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Volume |
183 |
Issue |
2 |
Pages |
408-418 |
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Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
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Abstract |
A novel lithium zinc niobium oxide LiZnNb(4)O(11.5) (LZNO) has been found in the Nb-rich part of Li(2)O-ZnO-Nb(2)O(5) system. LZNO, with an original alpha-PbO(2) related structure, has been synthesized by the routine ceramic technique and characterized by X-ray diffraction and transmission electron microscopy (TEM). Reflections belonging to the LZNO phase, observed in X-ray powder diffraction (XRPD) and electron diffraction, have been indexed as monoclinic with unit cell parameters a=17.8358(9)angstrom, b=15.2924(7)angstrom, c=5.0363(3)angstrom and gamma=96.607(5)degrees or as alpha-PbO(2)-like with lattice constants a=4.72420(3)angstrom, b=5.72780(3)angstrom, c=5.03320(3)angstrom, gamma=90.048(16)degrees and modulation vector q=0.3a*+1.1b* indicating a commensurately modulated alpha-PbO(2) related structure. The monoclinic cell is a supercell related to the latter. Using synchrotron powder diffraction data, the structure has been solved and refined as a commensurate modulation (superspace group P112(1)/n(alpha beta 0)00) as well as a supercell (space group P2(1)/b). The superspace description allows us to consider the LZNO structure as a member of the proposed alpha-PbO(2)-Z (3 + 1)D structure type, which unifies both incommensurately and commensurately modulated structures. HRTEM reveals several types of defects in LZNO and structural models for these defects are proposed. Two new phases in Li(2)O-ZnO-Nb(2)O(5) system are predicted on the basis of this detailed HRTEM analysis. (C) 2009 Elsevier Inc. All rights reserved. |
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Place of Publication |
London |
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Wos |
000274497600020 |
Publication Date |
2009-12-17 |
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ISSN |
0022-4596; |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
2.299 |
Times cited |
9 |
Open Access |
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Notes |
Iap-Vi |
Approved |
Most recent IF: 2.299; 2010 IF: 2.261 |
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Call Number |
UA @ lucian @ c:irua:95646 |
Serial |
3542 |
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Author |
Arakcheeva, A.; Pattison, P.; Chapuis, G.; Rossell, M.; Filaretov, A.; Morozov, V.; Van Tendeloo, G. |
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Title |
KSm(MoO4)2, an incommensurately modulated and partially disordered scheelite-like structure |
Type |
A1 Journal article |
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Year |
2008 |
Publication |
Acta crystallographica: section B: structural science |
Abbreviated Journal |
Acta Crystallogr B |
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Volume |
64 |
Issue |
Part 2 |
Pages |
160-171 |
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Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
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Abstract |
The incommensurately modulated scheelite-like KSm( MoO4)(2) structure has been refined in the monoclinic superspace group I2/b(alpha beta 0)00 by the Rietveld method on the basis of synchrotron radiation powder diffraction data. The systematic broadening of satellite reflections has been accounted for by applying anisotropic microstrain line-broadening. The microstructure has been studied by transmission electron microscopy (TEM). The partial disorder of the K and Sm cations in the A position is best approximated by a combination of harmonic and complex crenel functions with (0.952Sm + 0.048K) and (0.952K + 0.048Sm) atomic domains. This combination yields a compositional wave distribution from {KMoO4} to {SmMoO4} observed in the ab structure projection along q. The specific features of KSm(MoO4)(2) and degree of the A-cation ordering are discussed in comparison with the previously reported structure of KNd(MoO4)(2). |
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Place of Publication |
Copenhagen |
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Wos |
000253992600004 |
Publication Date |
2008-03-28 |
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ISSN |
0108-7681; |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
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Times cited |
23 |
Open Access |
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Notes |
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Approved |
Most recent IF: NA |
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Call Number |
UA @ lucian @ c:irua:102618 |
Serial |
3539 |
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