Thermoluminescence Characteristics of Natural Quartz and Synthesized Silica Glass Prepared by Sol-Gel Technique

Abstract

Aims: Study of thermoluminescence (TL) characteristics of natural quartz and synthesized quartz (silica glass synthesized by sol-gel technique) was investigated. Study Design: Studies TL properties of both types samples with different annealing temperatures, heating rates and doses actual samples experiment and an analysis of results. Place and Duration of Study: Department of Physics (Atomic Physics Lab's, The University of Jordan), between May 2012 to May 2014. Methodology: Natural  and synthesized quartz annealed at high temperatures exhibit crystalline of natural as indicated by x-ray diffraction spectra and amorphous structure of synthesized silica glass and converted partially to crystalline form by irradiation. Examination was facilitated by use of EDS and SEM to validate the results and conclusions. Results: TL-properties of quartz resulted in the formation of two TL-peaks centered near 150°C (P1) and 200°C (P2) whereas in synthesized glass, the detected peaks are centered near 150°C and about 300°C. Variations of the normalized TL intensity as function of the heating rate indicated reduction of TL-intensity accompanied by shift of TL-peaks towards higher temperatures. All glow (GL-) curve region was de-convoluted into five and six main peak components. Conclusion: The results show agreement with the available literature data. The main emission TL-peaks of SiO2 are largely associated with relaxation of excitons and oxygen defect sites related to shallow and deep trapping centers. The first peak, P1, is due to band-to-band transition of electrons from the minimum of the conduction band to the valence band maximum (VBM). The second Peak, P2, is attributed to relaxation of an exciton formed during ionization at a broken Si-O bond, and emission of self-trapped exciton occurs as a result of direct carrier re-combinations or via an oxygen vacancy. The other peaks, P3-P6, are associated with E΄-centers that form sub-band states extending from shallow to deep levels in the band gap of SiO2.