Scintillators are the backbone of high-energy radiation detection devices. Most scintillators are based on inorganic crystals that have applications in medical radiography, nuclear medicine, security inspection, dosimetry, and high-energy physics. In this paper, we present a new type of scintillator that is based on glass ceramics (composites of glasses and crystals). These scintillators are made from Eu2+-activated fluorozirconate glasses that are co-doped with Ba2+, La3+, Al3+, Na+, and Cl-. Subsequent heat treatment of the glasses forms BaCl2 nano-crystals (10-20 nm in size) that are embedded in the glass matrix. The resulting scintillators are transparent, efficient, inexpensive to fabricate, and easy to scale up. The physical structure and x-ray imaging performance of these glass-ceramic scintillators are presented, and an application of these materials to micro-computed tomography is demonstrated. Our study suggests that these glass-ceramic scintillators have high potential for medical x-ray imaging.
We investigated the energy-dependent scintillation intensity of Eu-doped fluorozirconate glass-ceramic x-ray detectors in the energy range from 6 to 20 keV. The experiments were performed at the Advanced Photon Source, Argonne National Laboratory. The glass ceramics are based on Eu-doped fluorozirconate glasses, which were additionally doped with chlorine to initiate the nucleation of BaCl2 nanocrystals therein. The x-ray excited scintillation is mainly due to the 5d-4f transition of Eu2+ embedded in the BaCl2 nanocrystals; Eu2+ in the glass does not luminesce. Upon appropriate annealing the nanocrystals grow and undergo a phase transition from a hexagonal to an orthorhombic phase of BaCl2. The scintillation intensity is investigated as a function of the x-ray energy as well as of the particle size and structure of the embedded nanoparticles. The scintillation intensity versus x-ray energy dependence shows that the intensity is inversely proportional to the photoelectric absorption of the material, i.e. the more photoelectric absorption the less scintillation.
X-ray storage phosphors have several advantages over traditional films as well as digital X-ray detectors based on thin-film transistors (TFT). Commercially used storage phosphors do not have high resolution due to light scattering from powder grains. To solve this problem, we have developed storage phosphor plates based on modified fluorozirconate (ZBLAN) glasses. The newly developed imaging plates are “grainless” and, therefore, can significantly reduce light scattering and improve image resolution. To study the structure and image performance of the novel storage phosphor plates, we conducted X-ray diffraction (XRD) and X-ray imaging analyses at the Advanced Photon Source, Argonne National Laboratory. The XRD results show that BaCl2 crystallites are embedded in the glass matrix. These crystallites enlarge and are under residual stress after heat treatment. The X-ray imaging study shows that these storage phosphor plates have a much better resolution than a commercially used storage phosphor screen. The results also show that some of the glass ceramics are high-resolution scintillators. Our study demonstrates that these fluorozirconate-based glass ceramics are a promising candidate for high-resolution digital X-ray detectors for both medical and scientific research purposes.