Radiation Dose Response of Ag-Doped Phosphate Glasses with Different Alkali Metal Compositions in the Host

Abstract

Introduction For many years, the radiophotoluminescence (RPL) of Ag-doped phosphate glass has been exploited in personal dosimeters. On exposure to X-ray, gamma ray, and high-intensity laser irradiations, the electrons and holes are captured by the Ag+ ions in the glass structure, thereby changing the Ag+ ions into Ag0 and Ag2+, respectively [1]. Thus, Ag-doped phosphate glasses enable the estimation of the exposure dose due to the correlation between the amount of irradiation and the relative intensity of luminescence of the Ag0 and Ag2+ ions excited with ultraviolet light. In a previous research, we found that the peak wavelengths of the RPL bands depend on the alkali metal species used [2]. In this study, we investigated the radiation dose response of various Ag-doped phosphate glasses, containing alkali metals as cations, to optimize their composition and develop a higher-performance dosimeter. Experimental Methods The glass samples were prepared according to a conventional melt-quenching method in air. The raw materials, AgCl and (LiPO3)n (Li/Ag), were mixed, loaded into an alumina crucible and melted at 1073 K, for 30 min, in an electric furnace. The melt was then quenched on a stainless steel plate at 573 K, which is below the glass transition temperature. The same operations were also performed for NaPO3 (Na/Ag), (KPO3)n (K/Ag)，RbH2PO4 (Rb/Ag)and CsH2PO4 (Cs/Ag) instead of LiPO3. The Ag concentration was 0.1 mol% for all samples. In addition, phosphate glasses with mixed alkali metals were prepared in the same manner Li/Na-Ag, K/Na-Ag, Rb/Na-Ag, and Cs/Na-Ag. The samples were irradiated at room temperature with X-rays using an X-ray tube operating at 40 mA and 40 kV. The PL (photoluminescence) and RPL properties were analyzed using both PL and RPL spectra and the temporal luminescence profiles. The PL and RPL spectra were collected using an F-7000 (Hitachi) fluorescence spectrometer. The temporal profiles were recorded using a DeltaFlex 3000U-TMK2 (Horiba). The absorption spectra were measured using a spectrophotometer (Hitachi U-3500). Results The RPL spectra of the various Ag- doped phosphate glasses, irradiated with a dose of 50-Gy X-rays, are shown in Fig. 1. The sample K/ Na-Ag shows two emission band peaks, observed at 550 nm and 680 nm, with excitation at 310 nm. The peak of K is also detected at 550 nm with a line shapesimilar to that of the sample K/Ag. On the other hand, the peak of K/ Na-Ag observed at 680 nm shows a line shape similar to that of Na/Ag . These results indicate that Na-K/Ag is composed of K/Ag and Na/Ag domains and that Na and K phosphate layers are separately formed around fluorescent centers.