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  1. Free, publicly-accessible full text available July 1, 2024
  2. Abstract The fabrication of ceramic scintillators by laser sintering is briefly reviewed and current limitations discussed. The experimental work focused on the fabrication and characterization of undoped and Pr-doped Lu 3 Al 5 O 12 (LuAG). X-ray diffraction (XRD) and Raman spectroscopy were used to characterize the structure of the sintered ceramics, with XRD results suggesting the absence of residual thermal stresses. Collectively, Raman results suggested the incorporation of Pr to affect the structure and its dynamics. Broadening the peaks of the ceramics in relation to those from the single crystal revealed the presence of structural disorder. Scanning electron microscopy revealed intergrain porosity thus explaining the lack of optical transparency. Energy-dispersive X-ray spectroscopy (EDX) measurements showed Pr to be homogeneously distributed. Radioluminescence measurements under X-ray excitation as a function of the temperature were used to investigate intrinsic defects of the host, including anti-sites and F-type defects. 
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  3. 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. 
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