Samarium-Doped Fluorochlorozirconate Glass-Ceramics as Red-Emitting X-Ray Phosphors

We have examined the photoluminescence (PL) and X-ray luminescence (XL) of fluorochlorozirconate (FCZ) glass-ceramics (FCZ-GC) doped with Sm3+ and Sm2+ ions. Sm-doped FCZ-GCs have been prepared by annealing a ZBLAN glass of nominal composition 53% ZrF4, 20% NaF, 3% AlF3, 3% LaF3, 1% SmF3, 1% BaF2, 19% BaCl2 (mol%) above the glass transition of the host glass matrix. SmF3 was added to the initial glass mix for trivalent samarium doping. Sm2+ doping was achieved by reducing Sm3+ to Sm2+ during the melting of the initial mix by the addition of NaBH4. FCZ-GC contains BaCl2 nanocrystals formed during the annealing with embedded Sm2+ ions, which dominate PL and XL. The PL of Sm2+ ions embedded in BaCl2 nanocrystals strongly depends on their crystal structure (hexagonal or orthorhombic) and may be used to identify that structure. The correlation of the PL spectra with X-ray diffraction data is used to estimate the size of nanocrystals. The nanocrystals with average dimensions <similar to 30 nm are mainly hexagonal while larger crystals are mostly orthorhombic. XL is more efficient in glass-ceramics containing relatively large BaCl2 nanocrystals with hexagonal crystal structure.