BeO OSL dosimeter: Its synthesis and luminescence mechanisms

Optically Stimulated Luminescence (OSL) is the luminescence observed during illumination of irradiated insulator or a wide band gap semiconductor. The OSL signals are measurable and informative about radiation dose. Beryllium Oxide (BeO) OSL dosimeters as ceramic chips have been well-known for many years. However, excluding the chemical, structural and thermoluminescence (TL) properties, until now, no work has been reported based on OSL properties of synthesized BeO nanophosphors in the literature. For this purpose, in order to promote the usage of the material in radiation measurements, in this study, BeO nanoparticles were synthesized and doped with some phosphors (Alumina and Calcium) by using sol-gel, polyacrylamide-gel and precipitation methods. In order to determine the crystalline phases of the produced materials, X-Ray Diffractometer analysis were performed. Additionally, surface morphological analysis were done by using Scanning Electron Microscope (SEM) to investigate the morphology and the particle size of the synthesized materials. On the other hand, Fourier Transform Infrared Spectrometer (FT-IR) analysis were carried out for all samples to observe the vibrational modes of functional groups of the produced phases. Furthermore, Differential Scanning Calorimetry (DSC) and Thermogravimetric (TG) Analysis were used for investigation the chemical and physical changes in/on material during temperature measurement. In this thesis, OSL measurements of undoped and doped BeO pellets were made using a "Risø TL/OSL reader (Model TL/OSL-DA-20)". The BeO pellets were irradiated with a beta source of 90Sr / 90Y mounted in the reader. The OSL decay curves for each material were demonstrated and analyzed for determining the OSL characteristics of dose response, fading, reusability and multireadability properties of BeO ceramic pellets studied. On the other hand, the minimum detectable dose (MDD) values of an OSL system for each material were calculated. In order to observe a relation between OSL and TL signals, TL signals and the effect of OSL measurements on TL signals were investigated. Thermal activation energies of the light sensitive TL peaks and the OSL signals were also calculated using various heating rate method and the results were compared with each other. As a result, these studies proved that the dosimetric properties of both undoped and doped BeO pellets to be distinguishable like well-known and commonly used ceramic chips (Thermalox 995) and shed light on the present literature to use extensively and develop this material for usage in dosimetry in the future. Keywords: Beryllium Oxide (BeO), Sol-Gel Synthesis Technique, Nanophosphors, Luminescence Dosimetry, Optically Stimulated Luminescence (OSL).