KEu(MoO4)2: Polymorphism, Structures, and Luminescent Properties

Vladimir A. Morozov, Alla V. Arakcheeva, Philip Pattison, Katrien W. Meert, Philippe F. Smet, Dirk Poelman, Nicolas Gauquelin, Johan Verbeeck, Artem M. Abakumov, Joke Hadermann

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)

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 923-1203 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 I1¯(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. (Figure Presented).

Original languageEnglish
Pages (from-to)5519-5530
Number of pages12
JournalChemistry of Materials
Volume27
Issue number16
DOIs
Publication statusPublished - 25 Aug 2015
Externally publishedYes

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