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Local Structural Effects of Eu 3+ Incorporation into Xenotime‐type Solid Solutions with Different Host Cations
Author(s) -
Xiao Bin,
Lösch Henry,
Huittinen Nina,
Schmidt Moritz
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201802841
Subject(s) - dopant , crystallography , crystal structure , luminescence , lattice (music) , materials science , spectroscopy , doping , ion , chemistry , molecular physics , physics , optoelectronics , quantum mechanics , acoustics , organic chemistry
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 LuPO 4 ) 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 LuPO 4 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 YPO 4 , whereas a small distortion of the crystallographic site in LuPO 4 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.