UV-Blue Emitting SiO2 Sintered Glass for Radiation Dosimetry

Abstract

Phosphor materials are often used in radiation measurement as a converter, from ionizing radiation to light. In dosimetry, a phosphor material absorbs and accumulates the incident radiation energy over a certain period of time as electronic charges trapped at localized centres. A recombination of these charges can be stimulated externally by light exposure or heat, followed by light emission. The latter emission intensity is proportional to the incident radiation dose accumulated, hence the radiation dose can be indirectly measured. Today, such phosphor materials are used in a variety of scenes, for example, personnel dose monitoring, radiation therapy, and medical imaging. In this study, we have synthesized bulk SiO2 glasses and characterized for dosimetry applications. The samples were prepared by spark plasma sintering (SPS), which is a unique way to obtain a bulk SiO2 glass. First, radioluminescence (RL) spectrum was measured for both the prepared sample and SiO2 single crystal. The glass sample showed a broad emission feature from 300 to 500 nm while the crystal sample showed a narrower emission around 450 nm. The RL measurement at low temperatures revealed that the broad emission by glass consists of two components with the peaks at 385 nm and 511 nm. The origin of the former emission seems to be a pair of silylene centres generated by sintering process while the latter is due to a presence of dioxasilirane and sililene. Moreover, it was found that the sample shows a strong thermally-stimulated luminescence (TSL) after X-ray irradiation. The glow curve indicates strong emissions at the temperatures of approximately 140 °C and higher than 300 °C. In contrast, SiO2 single crystal shows much weaker signal at lower temperature (~90 °C). The luminescent centres responsible for TSL are the silylene-silylene pair emitting at 385 nm. With a use of TSL in our SiO2 glass sample, a detectable X-ray dose range is at least 1 - 10000 mGy, which is a comparable sensitivity to commercial dosimeter.