Jean-Claude Bunzli - The luminescence of NaxEu(2-x)/33+MoO4 scheelites depends on the number of Eu-clusters occurring in their incommensurately modulated structure

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  Publication Details (including relevant citation   information):

  Arakcheeva,A., Logvinovich,D., Chapuis,G., Morozov,V.,   Eliseeva,S.V., Bunzli,J.C.G., Pattison,P. Chemical   Science 2012 3 (2) 384-390

  Abstract: Scheelite related compounds with   general formula M-n(XO4)(m) are the subject of hefty interest   owing to their optical properties, stability and relatively   simple preparation. Eu3+-containing scheelites are considered as   red-emitting phosphors and the main factors affecting their   luminescence are thought to be chemical composition and particle   size while the influence of their structure is generally ignored.   Here we report eight compounds from the NaxEu(2-x)/3MoO4 series   prepared by conventional solid-state reaction and present a   detailed analysis of their crystal structures. Six of them have   modulated structures, a common feature of SRCs, in which dopant   Eu3+ ions are orderly distributed. Moreover, different amounts of   Eu3+ dimers are detected in the modulated structures,   characterized by weak satellite reflections appearing in the   lower angle part of the XRD patterns. These reflections are   indexed and incorporated into Rietveld's refinement using   superspace (3 + 1)-dimension symmetry. The remarkable feature of   the compounds is that the characteristic luminescence parameters,   overall (Q(L)(Eu)) and intrinsic (Q(Eu)(Eu)) quantum yields,   Eu(D-5(0)) lifetimes, and sensitization efficiencies (eta(sens)),   correlate with the number of Eu3+ aggregates, but not directly   with the composition x of the materials. This provides an   efficient tool for understanding and controlling the luminescence   properties of scheelite related compounds

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