Luminescence and Scintillation in the Niobium Doped Oxyfluoride Rb[sub.4]Ge[sub.5]O[sub.9]F[sub.6]:Nb

• Published in: Inorganics 2022-06, Vol.10 (6)
• Main Authors: Carone, Darren, Klepov, Vladislav V, Misture, Scott T, Schaeperkoetter, Joseph C, Jacobsohn, Luiz G, Aziziha, Mina, Schorne-Pinto, Juliano, Thomson, Stuart A. J, Hines, Adrian T, Besmann, Theodore M, zur Loye, Hans-Conrad
• Format: Article
• Language: English
• Subjects: Analysis; Chemical synthesis; Crystals; Fluorides; Germanium; Methods; Niobium; Optical properties; Oxides; Rubidium; Structure
• ISSN: 2304-6740
• DOI: 10.3390/inorganics10060083

A new niobium-doped inorganic scintillating oxyfluoride, Rb[sub.4]Ge[sub.5]O[sub.9]F[sub.6]:Nb, was synthesized in single crystal form by high-temperature flux growth. The host structure, Rb[sub.4]Ge[sub.5]O[sub.9]F[sub.6], 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 Ge[sub.3]O[sub.9] units connected by GeO[sub.3]F[sub.3] octahedra. In its pure form, Rb[sub.4]Ge[sub.5]O[sub.9]F[sub.6] shows neither luminescence nor scintillation but when doped with niobium, Rb[sub.4]Ge[sub.5]O[sub.9]F[sub.6]:Nb exhibits bright blue luminescence and scintillation. The isostructural doped structure, Rb[sub.4]Ge[sub.5]O[sub.9]F[sub.6]: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.