Wydział Chemii

Mirosław Karbowiak

Jakub Cichos

Czesław Rudowicz

2016

Polyhedron

105

42-48

10.1016/j.poly.2015.11.044

Naukowa

Angielski

Artykuł

There exists a controversy in the hitherto reported studies concerning the actual space group that
accounts for spectroscopic results observed for the trivalent lanthanide (Ln3+) ions doped into
b-NaLnF4 hosts. The two competing assignments of the space group: P
6 or P63/m, bear on the associated
point symmetry groups, which describe the local site symmetry of the dopant Ln ions. This paper aims at
resolving this controversy. For this purpose two approaches are utilized. First, several new samples were
synthesized and characterized by photoluminescence (PL) spectroscopy. Both the emission and excitation
PL spectra have been measured. The analysis of the present experimental data indicates unequivocally
that the dopant Ln3+ ions enter the crystal lattice b-NaGF4 and b-NaYF4 at two crystallographically distinct
sites. Hence, the correct space group for these hosts is P
6 and not P63/m. The intricacies arising from
the sample preparation methods, which bear on the interpretation of the results, are also clarified.
Second, the theoretical modeling of the crystal-field parameters (CFPs) is carried out based on superposition
model to correlate the available crystallographic and spectroscopic data. The crystal-field analysis
enables to ascribe unambiguously the spectroscopically determined sites to the crystallographic sites 1a
and 1f. In this way an interpretation of photoluminescence spectra is achieved that fully corroborates the
available crystallographic data. The influence of structural disorder occurring in b-NaLnF4 family of
compounds on the 5D0?7F1 photoluminescence spectra of dopant Eu3+ ion and its role in interpretation
of experimental data is also discussed.

lanthanides, photoluminescence, structure elucidation, symmetry

http://dx.doi.org/10.1016/j.poly.2015.11.044

http://www.elsevier.com