CC BY
16LS-O-4
Structural and spectroscopic features of the rare-earth-doped bixbyite-type yttrium scandate
E. Dobretsova1, O. Alimov1, D. Guryev1, S. Rusanov1, V. Kashin1, S. Kutovoi1, V. Vlasov1, V. Voronov1, G. Kiriukhina2'3, S. Simonov4, Olga Yakubovich2, V. Tsvetkov1
1 - Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow 119991, Russia 2- M. V. Lomonosov Moscow State University, Leninskye Gory 1, Moscow 119991, Russia 3 - The Institute of Experimental Mineralogy, Russian Academy of Sciences, Chernogolovka 142432, Russia 4 - Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka 142432 Russia
elenadobretsova89@gmail.com, eadobr@kapella.gpi.ru
The yttrium scandate crystal fiber has been obtained through laser-heated pedestal growth (LHPG). Y2O3 and Sc2O3 powders of high purity were used as precursors.
The crystal structure has been characterized using X-ray diffraction on the powdered crystal fiber sample. The XRD pattern exhibits well-defined narrow peaks pointing to high crystallinity of the sample. According to X-ray powder diffraction data the yttrium scandate belongs to a bixbyite-type cubic structure with a space group Ia3 and unit cell parameters a = 10.228(1) Á.
A cubic Ia3 crystal structure of YScO3 has been refined using a single-crystal X-ray diffraction method. In the bixbyite-type structure, there are two symmetrically different positions for cations: 8b site (C31 symmetry) and 24d site (C2 symmetry). Two types of 6-vertex polyhedra (M1O6 and M2O6) statistically populated by Y3+ and Sc3+ cations in the almost equal ratio share corners and edges to form a chessboard packing, derived from the fluorite structure type [1, 2]. There are additional free cavities of octahedral shape in the structure that may serve as a reservoir for the insertion of rare-earth ions.
The spectral-kinetic characteristics of the rare-earth-doped YScO3 crystal fibers were measured under selective laser excitation and luminescence determination. Luminescence excitation spectra of the rare-earth doped crystal fibers include two neighboring lines at low temperature (T = 77 K). However,
the electric dipole - dipole transitions are forbidden for rare-earth ions placed in C3i sites due to
inversion symmetry, and the luminescence from these centers must be absent. Well-resolved fluorescence from two types of rare-earth local centers observed with comparable intensities might be responsible for decreasing of local symmetry due to the substitution of Y3+ and Sc3+ for rare-earth ions in the C3i site, or inclusion of the rare-earth ions in the octahedral voids between the basic polyhedra.
[1] P. Moore and T. Araki, Braunite; its structure and relationship to bixbyite, and some insights on the genealogy of fluorite derivative structures, American Mineralogist, vol. 61, pp. 1226-1240, (1976).
[2] O. Alimov, E. Dobretsova, D. Guryev et al., Growth and characterization of neodymium-doped yttrium scandate crystal fiber with a bixbyite-type crystal structure. Crystal Growth & Design, vol. 20, pp. 4593-4599, (2020).
