A new niobium-doped inorganic scintillating oxyfluoride, Rb4Ge5O9F6:Nb, was synthesized in single crystal form by high-temperature flux growth. The host structure, Rb4Ge5O9F6, crystallizes in the orthorhombic space group Pbcn with lattice parameters a = 6.98430(10) Å, b = 11.7265(2) Å, and c = 19.2732(3) Å, consisting of germanium oxyfluoride layers made up of Ge3O9 units connected by GeO3F3 octahedra. In its pure form, Rb4Ge5O9F6 shows neither luminescence nor scintillation but when doped with niobium, Rb4Ge5O9F6:Nb exhibits bright blue luminescence and scintillation. The isostructural doped structure, Rb4Ge5O9F6:Nb, crystallizes in the orthorhombic space group Pbcn with lattice parameters a = 6.9960(3) Å, b = 11.7464(6) Å, and c = 19.3341(9) Å. X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) measurements suggest that the niobium is located in an octahedral coordination environment. Optical measurements inform us that the niobium dopant acts as the activator. The synthesis, structure, and optical properties are reported, including radioluminescence (RL) measurements under X-ray irradiation.

Single crystals of two new germanates, [(Rb6F)(Rb4F)][Ge14O32] and [(Rb6F)(Rb3.1Co0.9F0.96)][Co3.8Ge10.2O30F2], were synthesized via high temperature RbCl/RbF flux growth. Both compounds crystallize in the cubic space group F4 ̅3m and possess the...

The crystal chemistry and magnetic properties for two triple perovskites, BaFeIrO and BaNiIrO, grown as large, highly faceted single crystals from a molten strontium carbonate flux, are reported. Unlike the idealized AMM'O hexagonal symmetry characteristic of most triple perovskites, including BaNiIrO BaFeIrO possesses significant site-disorder, resulting in a noncentrosymmetric polar structure with trigonal symmetry. The valence of iron and iridium in the heavily distorted Fe/Ir sites was determined to be Fe(III) and Ir(V) by X-ray absorption near edge spectroscopy (XANES). Density functional theory calculations were conducted to understand the effect of the trigonal distortion on the local Fe(III)O electronic structure, and the spin state of iron was determined to be S = 5/2 by Mössbauer spectroscopy. Conductivity measurements indicate thermally activated semiconducting behavior in the trigonal perovskite. Magnetic properties were measured and near room temperature magnetic ordering (T = 270 K) was observed for BaFeIrO.

Single crystals of four new germanate framework structures were synthesized via the flux growth method. Rb 2 Cu 3 Ge 5 O 14 and Cs 2 Cu 3 Ge 5 O 14 crystallize in the triclinic space group P1̅ with lattice parameters of a = 6.23840(10) Å, b = 7.175(2) Å, c = 7.8731(2) Å, α = 82.1540(10)°, β = 71.6150(10)°, and γ = 80.7040(10)°for the Rb analogue and a = 6.3626(3) Å, b = 7.2272(3) Å, c = 7.9360(4) Å, α = 82.285(2)°, β = 70.978(2)°, and γ = 80.619(2)°for the Cs analogue. Cs 7 Cu 2 Ge 11 O 27 F crystallizes in a new structure that adopts the orthorhombic space group Pmma with lattice parameters a = 20.0462(4) Å, b = 10.9087(2) Å, and c = 7.66080(10) Å. The fourth structure, [(Cs 6 F)(Cs 3 AgF)][Ge 12 Mn 2 O 32 ], crystallizes in the cubic space group F4̅ 3m with a lattice parameter of 15.5197(4) Å and is structurally related to a Ge 7 O 16 family of zeotypes. The syntheses and structures of the four compounds are reported. The assignment of square planar versus octahedral coordination for the Cu 2+ coordination sites in this structure type is commented on, as is the impact of subtle synthetic changes on the formation of the specific structures in this phase space.