High- and very-high-dose dosimetry using silicate minerals

Photoluminescence and thermoluminescence properties of Eu2+ doped and Eu2+ ,Dy3+ co-doped Ba2 MgSi2 O7 phosphors

In this work, we report the preparation, characterization, comparison and luminescence mechanisms of Eu²⁺ -doped and Eu²⁺ ,Dy³⁺ -co-doped Ba₂ MgSi₂ O₇ (BMSO) phosphors. Prepared phosphors were synthesized via a high temperature solid-state reaction method. All prepared phosphors appeared white. The phase structure, particle size, and elemental analysis were analyzed using X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy-dispersive X-ray (EDX) analysis. The luminescence properties of the phosphors were investigated by thermoluminescence (TL) and photoluminescence (PL). The PL excitation and emission spectra of Ba₂ MgSi₂ O₇ :Eu²⁺ showed the peak to be around 381 nm and 490 nm respectively. The PL excitation spectrum of Ba₂ MgSi₂ O₇ :Eu²⁺ Dy³⁺ showed the peak to be around 341 nm and 388 nm, and the emission spectrum had a broad band around 488 nm. These emissions originated from the 4f⁶ 5d¹ to 4f⁷ transition of Eu²⁺ . TL analysis revealed that the maximum TL intensity was found at 5 mol% of Eu²⁺ doping in Ba₂ MgSi₂ O₇ phosphors after 15 min of ultraviolet (UV) light exposure. TL intensity was increased when Dy³⁺ ions were co-doped in Ba₂ MgSi₂ O₇ :Eu²⁺ and maximum TL intensity was observed for 2 mol% of Dy³⁺ . TL emission spectra of Ba_1.95 MgSi₂ O₇ :0.05Eu²⁺ and Ba_1.93 MgSi₂ O₇ :0.05Eu²⁺ ,0.02Dy³⁺ phosphors were found at 500 nm. TL intensity increased with UV exposure time up to 15 min, then decreased for the higher UV radiation dose for both Eu doping and Eu,Dy co-doping. The trap depths were calculated to be 0.54 eV for Ba_1.95 MgSi₂ O₇ :0.05Eu²⁺ and 0.54 eV and 0.75 eV for Ba_1.93 MgSi₂ O₇ :0.05Eu²⁺ ,0.02Dy³⁺ phosphors. It was observed that co-doping with small amounts of Dy³⁺ enhanced the thermoluminescence properties of Ba₂ MgSi₂ O₇ phosphor. Copyright © 2016 John Wiley & Sons, Ltd. [Correction added on 5 April 2016, after first online publication: The following parts of the abstract have been edited for consistency. '4f65d1' has been corrected to '4f⁶ 5d¹ ', '4f7' has been corrected to '4f⁷ ', 'Ba1.95' has been corrected to 'Ba_1.95 ' and 'Ba1.93' has been corrected to 'Ba_1.93 ' respectively.].

Radiation dosimetry using decreasing TL intensity in a few variety of silicate crystals

This study shows that there are some ionic crystals which after irradiation with high gamma dose Dm and subsequent irradiation with low doses ranging up to 500Gy present a decreasing TL intensity as dose increases. This interesting feature can be used as a calibration curve in radiation dosimetry. Such behavior can be found in green quartz, three varieties of beryl and pink tourmaline. In all these silicate crystals it can be shown that irradiation with increasing γ-dose there is a dose Dm for which the TL intensity is maximum. Of course, Dm varies depending on the crystal and irradiated crystal with the dose Dm is stable. If one of these crystals is taken and irradiated with doses from low values up to 400-500Gy, a curve of decreasing TL intensity is obtained; such a curve can be used as a calibration curve.