Local Structural Effects of Eu3+ Incorporation into Xenotime‐type Solid Solutions with Different Host Cations. Issue 50 (13th August 2018)

• Record Type: Journal Article
• Authors: Xiao, Bin; Lösch, Henry; Huittinen, Nina; Schmidt, Moritz
• Is Part Of: Chemistry. Volume 24:Issue 50(2018)
• Page Start: 13368
• Page End: 13377
• Publication Date: 2018-08-13
• Subjects: europium -- ion incorporation -- luminescence -- time-resolved laser luminescence spectroscopy (TRLFS) -- xenotime single crystals; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201802841
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: In this study, the effect of host cations on the local structure around the dopant site of materials from the xenotime family is systematically studied on the molecular level. A series of six Eu 3+ ‐doped xenotime‐type single crystals (Tb, Y, Ho, Er, Yb, and LuPO4 ) have been grown and spectroscopically analyzed by using polarization‐dependent laser‐induced luminescence spectroscopy (p‐TRLFS). Our results demonstrate that the structural disorder changes in a non‐linear manner with a structural break between Yb 3+ and Lu 3+ . Despite adopting identical crystal structures, the solid solutions of these materials vary significantly, and differ from monazite solid solutions. Similar Eu 3+ incorporation behavior with a strongly distorted dopant site is found for the early members of the xenotime family, whereas LuPO4 with the largest host versus dopant radii mismatch is anomalous in that it contains the most symmetrical lattice site. This goes along with a significantly stronger crystal field, indicating a shorter Eu−O bond length, as well as a strong vibronic coupling to external translational lattice vibrations. The p‐TRLFS analysis confirms the breakdown of the crystallographic site symmetry from D 2 d to C 1 in YPO4, whereas a small distortion of the crystallographic site in LuPO4 results in an S 4 point symmetry for the Eu 3+ cation. The lattice with the smallest cation host site is no longer sufficiently flexible to make room for Eu 3+ and instead "forces" the guest ion to occupy a less distorted Lu 3+ site. Abstract : Better with europium : A series of europium‐substituted xenotime bulk single crystals, LnPO4 (Ln=Tb, Y, Ho, Er, Yb, and Lu), were prepared and systematically characterized by polarization‐dependent time‐resolved laser luminescence spectroscopy (p‐TRLFS). The polarized spectra demonstrate the dependence of the dopant site symmetry on the difference in the ionic radii of the host cations (see scheme).