Electron paramagnetic resonance study of Fe3+ ions at octahedral and tetrahedral mirror symmetry sites in the LiScGeO4 crystal

Abstract

An electron paramagnetic resonance (EPR) study of a synthetic single crystal of LiScGeO• doped with Cr ions earried out earlier at the X-and Q-bands at 300 K has indicated additional weak lines. A detailed analysis of these EPR lines, which were tentatively attributed to the Fe 3+ ions at two different mirror symmetry sites, is presented in this paper. The angular dependences in the three crystallographic planes were resolved by fitting the two distinct spectra denoted Fe3+(l) and Fe3+(II) with a spin Hamiltonian (S = 5/2) of monoclinic symmetry. The rank-4 crystal field tensors at tetrahedral and octahedral sites were calculated with the point-charge model to determine the principal axis ofientations of their cubic, letragonal and trigonal components. A comparative analysis of the zero-field splitting tensors and the crystal field ones indicates that Fe3+(I) ions substitute for Sc 3 § at octahedral sites and Fe3+(II) ions substitute for Ge 4~ at tetrahedral sites with no significant distortion of the coordination polyhedra in the structure of LiScGeO 4. IntroduetionThe structure of LiScGeO 4 belongs to the orthorhombic space group D~ 6 Pnma with a = 1.0673 nm, b = 0.59926 nm, c = 0.49667 nm [1]. Fe 3+ ions in low concentrations ate usual traces in the natural and synthetic crystals with olivine type structure thus determining their spectroscopic properties. In forsterite Mg2SiO a, Fe 3+ ions were established as substituting at all the three structurally nonequivalent cationic sites [2, 3]: the octahedral MI (4a) and M2 (4c) sites, and the tetrahedral (4c) sites. In chrysoberyl A12BeO 4, Fe 3+ ions were established as substituting for Al 3+ at the octahedral M2 site [4]. Previously we have reported [5] that in the Cr-doped crystal of LiScGeO 4, along with electron paramagnetic reso-

Ultraviolet-A Persistent Luminescence of a Bi3+-Activated LiScGeO4 Material

“…The [LiO 6 ] and [ScO 6 ] octahedra and [GeO 4 ] tetrahedron compose the crystal cell in this crystal structure (Figure 1b). 32 In this host, first, because of the same valence state and similar ionic radii of Bi 3+ (r = 1.03 Å) and Sc 3+ (r = 0.75 Å) under the same coordination environment (CN = 6), 33,34 the doped Bi 3+ ions may occupy the Sc 3+ sites. Then, the further increased Bi 3+ ions may enter into the Li + sites (r = 0.76 Å; CN = 6), which may offer a possible chance to form the Bi2+ Li defect as an effective trap that can contribute to PersL.…”

“…62). The [LiO 6 ] and [ScO 6 ] octahedra and [GeO 4 ] tetrahedron compose the crystal cell in this crystal structure (Figure b) . In this host, first, because of the same valence state and similar ionic radii of Bi 3+ ( r = 1.03 Å) and Sc 3+ ( r = 0.75 Å) under the same coordination environment (CN = 6), , the doped Bi 3+ ions may occupy the Sc 3+ sites.…”

Exploring Intrinsic Electron-Trapping Centers for Persistent Luminescence in Bi3+-Doped LiREGeO4 (RE = Y, Sc, Lu): Mechanistic Origin from First-Principles Calculations

“…LiREGeO 4 (RE = Sc, Y, Lu) crystallizes into the orthorhombic Pnma space group (No. 62) and is composed of corner- and edge-sharing [LiO 6 ] and [REO 6 ] octahedra and [GeO 4 ] tetrahedra (Figure a). , The crystal was modeled by a periodic 1 × 2 × 2 supercell containing 112 atoms, where a dopant Bi or an intrinsic point defect was incorporated. We only considered isolated defects and ignored defect–defect interaction, which could be justified due to the high temperature employed for material synthesis.…”

“…1a). 14,21 The crystal was modeled by a periodic 1 × 2 × 2 supercell containing 112 atoms, where a dopant Bi or an intrinsic point defect was incorporated. We only considered isolated defects and ignored defect−defect interaction, which could be justified due to the high temperature employed for material synthesis.…”