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Synthesis and Thermoluminescence of New ZnO Phosphors C. Cruz-Vázquez 1, H. A. Borbón-Nuñez 1, V. R. Orante-Barrón 1, S. E. Burruel-Ibarra 1, V. M. Castaño 2 and R. Bernal 3 1

Departamento de Investigación en Polímeros y Materiales, Universidad de Sonora, Apartado Postal 130, Hermosillo, Sonora 83000 México 2 Centro de Física Aplicada y Tecnología Avanzada, Instituto de Física de la Universidad Nacional Autónoma de México, Apartado Postal 1-1010, Querétaro, Querétaro 76000 México 3 Departamento de Investigación en Física, Universidad de Sonora, Apartado Postal 5-088, Hermosillo, Sonora 83190 México

ABSTRACT In this work, the synthesis and thermoluminescence properties of new ZnO phosphors obtained by a chemical method are reported. Some samples were exposed to beta particle irradiation for doses ranging from 10.0 up to 6,400 Gy, and it was found that the thermoluminescence response as a function of dose is linear for doses below 200 Gy, and sublinear with no saturation clouds for greater doses. A broad shape glow curve with maximum located above 230 °C, that shifts to lower temperatures as dose increases, indicating that second order kinetics thermoluminescence processes are involved. The lower detection limit was estimated to be 13 Gy. We conclude that the phosphors under study are promising to develop dosimeters for high dose radiation dosimetry. INTRODUCTION Zinc oxide (ZnO) is a direct gap semiconductor with many attractive features for optoelectronic applications [1]. On the other hand, thermally stimulated luminescence, commonly termed thermoluminescence (TL), is widely accepted as an useful and reliable technique to study defects in insulators and semiconducting materials, but its more widely spread and successful application is in the field of radiation dosimetry [2-4]. ZnO exhibits TL under irradiation by different sources and striking radiation hardness. Moreover, ZnO is inert to environmental conditions, non-toxic, and insoluble in water. In spite of these features, there are only few reports concerning its potential application in radiation dosimetry. The lack of interest in ZnO as a dosimetric phosphor is due perhaps to the other important applications of this semiconductor, and to the low TL emission efficiency reported for samples previously studied [5-8]. Nowadays, because the increasing number of applications in science and technology involving the use of radiations, it is necessary to carry out research work focused to the development of new dosimetric materials tailored for distinct fields of radiation and dose intervals. The number of materials for high dose dosimetry (doses greater than 100 Gy) is limited, since at such doses many materials suffer from severe superlinearity, which can lead to an overestimation of the delivered dose [3]. The properties of a given material strongly depend upon the procedure followed to produce it. We have recently reported the synthesis and thermoluminescence characterization of new

pellet-shaped ZnO nanophosphors, obtained by thermal annealing of ZnS powder p