We report the results from a study of europium-doped fluorochlorozirconate glasses that have been thermally processed to induce nucleation and crystallization of BaCl2 crystallites. The resulting glass ceramics show a photostimulated luminescence (PSL) effect with a conversion efficiency which is up to 80% of that found in the commercial crystalline x-ray storage phosphor material BaFBr:Eu2+. Thermal processing for 20 min in the range 240–260 °C produces small (∼6–11nm) hexagonal BaCl2 crystallites, while temperatures in the range 270–290 °C lead to the formation and growth of larger (∼15–100nm) orthorhombic BaCl2 crystallites, as well as additional unidentified phases. We observe only weak PSL from glass ceramics containing hexagonal BaCl2 (∼0.1% conversion efficiency compared to BaFBr:Eu2+ at room temperature), but orthorhombic phase crystallites give rise to a much larger relative efficiency that increases with particle size, and reaches ∼80% for 100 nm diameter particles. The PSL is attributed to the excitation of electrons trapped as F centers in the BaCl2 crystallites, while the dependence on crystallite size is consistent with a PSL-inert surface shell of thickness ∼7nm surrounding the BaCl2 crystallites.

We report the synthesis of Eu2+- and chlorine-doped fluorozirconate glass-ceramics that show an intense photostimulated luminescence (PSL) after x-ray irradiation at room temperature. The PSL efficiency is up to 80% of that found in the well-known crystalline x-ray storage phosphor BaFBr:Eu2+, and it is the largest thus far reported for a glass-ceramic. We attribute the PSL to crystallites of orthorhombic BaCl2 that are formed after annealing above the glass temperature. Hexagonal BaCl2 crystallites are also observed after short annealing times, but they do not provide a measurable PSL signal. The photoluminescence peak from glass-ceramics containing orthorhombic BaCl2 crystallites occurs at 402 nm, and the stimulation band is centered at about 560 nm.

The measurement of spatially resolved high doses in microbeam radiation therapy has always been a challenging task, where a combination of high dose response and high spatial resolution (microns) is required for synchrotron radiation peaked around 50 keV. The x-ray induced Sm3+ → Sm2+ valence conversion in Sm3+ doped fluorophosphates glasses has been tested for use in x-ray dosimetry for microbeam radiation therapy. The conversion efficiency depends almost linearly on the dose of irradiation up to ∼5 Gy and saturates at doses exceeding ∼80 Gy. The conversion shows strong correlation with x-ray induced absorbance of the glass which is related to the formation of phosphorus-oxygen hole centers. When irradiated through a microslit collimator, a good spatial resolution and high “peak-to-valley” contrast have been observed by means of confocal photoluminescence microscopy.

No abstract