Synthesis and Evaluation of Photoluminescence and Scintillation Characteristics of Sn Doped HfO2–Al2O3–SiO2 Glasses
Authors: Shiratori Daiki , Nakauchi Daisuke , Nishikawa Akihiro , Fukuchi Yutaka , Yanagida Takayuki 
Published: December 2024

One of the ways to measure ionizing radiation is achieved by the process of converting high energy radiation into a large number of photons. To convert the ionizing radiation to photons, phosphors called a scintillator have been used. Recently, glasses have become attractive materials owing to their prominent advantages, such as low cost and easy formability, and these advantages are preferable for manufacturing scintillators. However, glass scintillators suffer from a rather low energy transfer efficiency under ionizing radiation irradiation, which results in a low light yield compared with single crystalline scintillators. Furthermore, glasses generally have a low density, which cause a reduction in X-ray absorption efficiency than single crystals. In this study, to achieve development the glass scintillator which have high sensitivity for X-rays and light-yield, we focused on Hf-containing silicate glass. Hf-based materials have only been studied mainly in the form of single crystals or ceramics, and the development of Hf- based materials into glass has not yet been reported. Recently, we have succeeded in synthesizing HfO2–Al2O3–SiO2 glasses and have reported the optical and luminescence properties of these glasses when Ce is doped. In the case of the Ce doping, the photoluminescence (PL) quantum yield (QY) was ~20% and the scintillation light yield was only a few hundred ph/MeV, indicating that there is room for improvement. Thus, to improve luminescence performance, we focused on Sn, which is known to show high luminescence efficiency in glass as a luminescent center. In this study, we have synthesized and investigated optical, photoluminescence, and scintillation properties of 10HfO2–10Al2O3–80SiO2 with various concentration of Sn, therefore, we will report these results and discussions in our presentation.

The glass samples were synthesized by using a floating-zone (FZ) melting furnace. HfO2 (3N, Rare Metallic Co., LTD.), Al2O3 (4N, High Purity Chemicals), SiO2 (4N, Rare Metallic Co., LTD.), and SnO (2N、High Purity Chemicals) were used as raw powders, and the materials were mixed homogeneously using a mortar. The mixed powders were formed into rod shapes by applying hydrostatic pressure and sintered in an electric furnace at 1200 ºC for 8 hours to obtain the sintered compacts. The sintered compacts were loaded into an FZ-method melting furnace, and glass samples were obtained by melting and quenching it.

The samples were evaluated by density measurement, differential thermal analysis, and X-ray diffraction measurement for physical properties and structural analysis, and Raman spectra, transmission spectra, PL excitation and emission spectra, PL absolute QY, and PL decay curves were measured for optical property evaluation. Scintillation spectra and scintillation decay curves under X-ray irradiation were measured for samples that exhibited luminescence, and pulse height spectra were also measured as an evaluation of scintillation light yield.

Only the emission characteristics are outlined here. All of the synthesized glass samples showed emission attributed to Sn2+, and their tendency to increase PL QY with increasing Sn concentration. X-ray induced scintillation spectra showed the characteristic emission bands of Sn2+ peaking at around 390 nm as well as the PL spectra. The peak wavelength of the spectrum shifts to the longer wavelength side with increasing Sn concentration in the glass. The disappearance of the short wavelength emission component with increasing Sn concentration in the glass can be attributed to self-absorption by Sn2+. The estimated scintillation light yield from pulse height spectrum measurements under γ-ray (137Cs) irradiation (Figure) was ~420 ph/MeV, approximately 10% of the GS10 glass scintillator counterpart.

Figure 1