Review of development of a silica-based thermoluminescence dosimeter

Development of a silica-based material suitable for thermoluminescence dosimetry (TLD) is described. Doped silica samples were prepared in-house using the sol-gel technique. Results from a micro-X-ray fluorescence (μ-XRF) study of Zn-doped silica have confirmed the capability of the sol-gel processing steps in producing homogeneously doped samples. The ability of sol-gel processing in producing doped samples with different dopant charge states has been illustrated in the case of copper (I)- and copper (II)-doped silica samples. The charge states of the dopants have been verified using the technique of X-ray absorption near-edge structure (XANES). X-ray diffraction (XRD) investigations have shown the structure of samples doped with erbium, copper (I) and copper (II) (listed in order of decreasing effect) to be altered by the dopants, albeit with the samples remaining in an amorphous state. Local structure studies, carried out using the method of extended X-ray absorption fine structure (EXAFS), reveal that in most cases the local environment of the dopant is similar to the respective native structure of the respective metal oxides. Conversely, in a number of cases, the dopant atoms occupy the silicon sites in the silica tetragonal geometry. Thermoluminescence (TL) studies were carried out on aluminium, copper (I), germanium, manganese, tin, and zinc-doped silica samples. Weight for weight, the most sensitive thermoluminescent material was found to be 4.0 mol% aluminium-doped silica, providing ∼3.5 times the TL yield of TLD100 and ∼5.4 times that of germanium-doped silica. The photon dose response of aluminium-doped silica was observed to be linear over the range of investigated dose, 0.5-10.0 Gy.