UV Induced Thermoluminescence in Rare Earth Oxide Doped Phosphors: Possible Use for UV Dosimetry

Abstract

UV induced thermoluminescent (TL) phenomena in some phosphors doped with rare earth oxides (Gd₂O₃:Eu, Gd₂O₃:Tb, Gd₂O₃:Dy and Y₂O₃:Eu) have been investigated. Gd₂O₃:Eu and Y₂O₃:Eu have been found to possess prominent TL phenomena. A stable high temperature glow peak has been found at 345 ^oC in the cubic (C type) crystalline structure of Gd₂O₃:Eu. A more stable high temperature glow peak has also been found at about 380 ^oC in Y₂O₃:Eu. The sensitivity is high enough to be used as UV sensors. TL phenomena in Gd₂O₃:Tb and Gd₂O₃:Dy have also been investigated, but their TL intensities are much weaker than that of Gd₂O₃:Eu or Y₂O₃:Eu. On the other hand, all glow peaks of Gd₂O₃:Tb and Gd₂O₃:Dy are unstable at room temperature, therefore, Gd₂O₃:Tb and Gd₂O₃:Dy are not suitable for use as UV detectors. According to the above properties, the C type (cubic) crystalline structure of the Gd₂O₃:Eu phosphor seems to possess the potential of being the TL material for UV measurement. The position of the high temperature glow peak depends on the total UV exposure. It locates at about 380 ^oC when this phosphor was irradiated by 302 nm UV at 2.4 mJ.cm^-2 exposure, but it shifts to 345 ^oC at 19.2 mJ.cm^-2 or higher exposure. The response curves of this phosphor for various wavelengths, e.g. 253.7 nm, 302 nm, and 365 nm, were also measured. This phosphor is sensitive enough to measure background UV radiations, such as sunlight, bulb light, etc.