Thermoluminescent characteristics of UV-irradiated Aluminum nitride (AlN).

This paper presents results of studying the thermoluminescence (TL) properties of aluminum nitride (AlN) synthesized by chemical vapor deposition (CVD) method. Previously to study the TL properties, the phosphor was characterized by means of X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FT-IR), photoluminescence (PL), and electron microscopy (EDS-SEM). TL studies were performed after ultraviolet (UV) irradiation using the whole spectrum of the xenon (Xe) lamp. XRD results show that AlN has a hexagonal crystalline structure. EDS-SEM analysis revealed the presence of oxygen (O) and Carbon (C) impurities in the powders. FT-IR spectroscopy lets us discuss the distribution of these impurities in the crystalline structure. The sample with 9.54% of C and 7.36% of O exhibits a TL glow curve with a predominant peak around 450 K, and according to the deconvolution method was found that the glow curve is composed by six peaks each one centered at 383, 446, 478, 540, 587 and 637 K. The TL response as a function of dose fits a logarithmic increasing function along the dose range studied: These results suggest that AlN is a promising material for application as a TL dosimeter for UV radiation.

Calculation of the half life for the thermoluminescent signal of Beryllium oxide.

Half-life is one of the fundamental parameters to characterize the thermoluminescent (TL) response in ionizing radiation dosimetry. In general, there are two types of important half-lives to model the phenomenon of thermoluminescence (TL). The first type of half-life is the time required for the concentration of trapped charge carriers in a single trap to decrease to half its initial value; this type of half-life is generally denoted as τ1/2. Experimentally, the loss of charge carriers and the corresponding half-life τ1/2 are not usually measured directly, but rather the intensity of the TL signal is measured at time t after the start of the experiment. The second type of half-life is the time required for the intensity of the TL to decay to half its initial value. This second type of half-life it is denoted by t1/2. Results of calculating the t1/2 half-life of the glow peaks of gamma irradiated BeO are presented. Calculations were made using the expressions derived in previous papers. To make this, the kinetic parameters (order of kinetics, activation energy and frequency factor) were previously determined. Results obtained could be useful in practical situations encountered in medical physics dosimetry.

Photoluminescence of gamma-irradiated Beryllium oxide.

This study analyses the emission and excitation spectra of Beryllium Oxide (BeO) unirradiated and irradiated with 60Co gamma radiation because of its potential use in radiation dosimetry. Deconvolution of the spectra showed that using an excitation wavelength λexc = 330 nm, four emission bands centered at 404, 430, 468 and 545 nm are obtained; These emission bands appear in both irradiated and non-irradiated BeO; however, the irradiated samples exhibited an extra emission band centered at 416 nm. The excitation spectrum was obtained by setting the emission monochromator at a wavelength λ0 = 400 nm. By means of deconvolution, it was obtained that the emission spectrum of the non-irradiated samples is constituted by two bands centered at 307 and 331 nm, while for the irradiated samples the spectrum has three components centered at 297, 334 and 317 nm. In addition, it was found that the area under the curve of all emission bands decreases after irradiation, this may be due to the formation of electron-hole pairs after irradiation, which have the effect of reducing radiative phenomena, which it could be favorable for the applications of BeO in ionizing radiation dosimetry.

Present status and future trends in the development of thermoluminescent materials.

There is a continuous growing interest in developing materials for TL radiation dosimetry, especially in the fields of medical, environmental and personal applications. Although several phosphors are being used in these fields today, many efforts are being made in order to develop new TL materials, having better tissue equivalence, and increased sensitivity to gamma radiation, high energy photons, electrons, neutrons and heavy ions. Different preparation methods and properties of several TL materials have been studied so far and it is found that many of these materials constitute a class of TL phosphors with good performances, especially when they are doped with suitable activators. Most widely used and extensively studied materials for TL dosimetry (TLD) are fluorides, sulfates, borates and sulfides of alkali and alkaline earth elements. Besides these, have been developed other phosphors based on metal oxides and mixtures of metal oxides, halo sulfates and different kinds of glasses and perovskites. In this paper, a review of the status and future trends in the development of TL materials is presented.