A Comprehensive Review on Rare-Earth Based Thermoluminescence Phosphors for Radiation Dosimetry

When ionizing radiation is incident on an insulating crystal, some of the deposited energy is stored in the lattice at defect sites, colour centres, etc. Upon heating the crystal, this stored energy is released and a fraction of it may be emitted as visible light. This is called ‘Thermoluminescence.’ Within certain limitations, the amount of light emitted is proportional to the radiation dose previously absorbed by the TL material. The application of thermoluminescence (TL) as a methodology for radiation dosimetry of ionizing radiation has been well-established since several decades and has found number of practical applications in various fields, such as personnel and environmental monitoring, retrospective dosimetry, medical dosimetry, space dosimetry, high-dose dosimetry, etc. Especially, alkaline-earth silicates are appropriate compounds as radiation detectors due to their high chemical stability. Doping may either cause the formation of new defect centers or recovering of existing levels within the band-gap for a defective host which changes both the optical and electronic features of the materials. Therefore, it is of great importance by choosing both the dopant as well as the host for thermoluminescence application. It has already been reported that commercially available thermoluminescence phosphor suffers from fading, stability, etc., which justifies the ongoing need to identify factors that can be exploited to make a thermoluminescence phosphor with high efficiency and stability.