ABSTRACT
Phosphors composed of Gd1-xRExAlO3 (0≤x ≤ 5 RE = Dy or Pr) stoichiometries were synthesized using the reverse coprecipitation pathway. The thermoluminescent responses of all phosphors were studied under beta radiation exposure. Doping the gadolinium aluminate host improved the thermoluminescent response of the phosphors, with the phosphors composed of Gd0.99Dy0.01AlO3 and Gd0.95Pr0.05AlO3 being the most sensitive. The Dy3+ ions produced a higher improvement of the thermoluminescent signal than the Pr3+ ions. Additionally, a proportional relationship between the similarity of the atomic numbers of the dopant and replaced ions and the sensitivity to thermoluminescence was confirmed. Besides, a slight shift of the thermoluminescent peaks toward lower temperatures was detected for doped phosphors. In the repeatability tests applied to the phosphor composed of Gd0.99Dy0.01AlO3, an anomalous increase in sensitization was observed. The observed sensitization was associated with the formation of electron trap clusters resulting from the continuous exposure to beta radiation. Furthermore, another sensitization phenomenon was detected in the phosphor with Gd0.95Pr0.05AlO3 stoichiometry when it was heated at low temperatures. The aforementioned striking behavior was related to quasi-continuous distributions of electron traps and the tunneling effect. In regard to linearity, the phosphor composed of Gd0.99Dy0.01AlO3 exhibited a linear response with the dose across the entire range of beta doses. However, the response of the Gd0.95Pr0.05AlO3 phosphor lost linearity beyond 26.4 Gy of beta dose. The results obtained through the use of the Tmax-Tstop method and deconvolutions suggested an enhancement in the efficiency of the thermoluminescent mechanisms due to the incorporation of activators.
ABSTRACT
The suitable choice of an activator and host combination is essential for synthesizing very sensitive thermoluminescence phosphors. In addition, conspicuous synthesis variables must be optimized to achieve the maximal response. The research presented herein shows that the most recommendable conditions to improve the thermoluminescence response of beta irradiated Gd1-xEuxAlO3 phosphors were: x = 0.02 for europium stoichiometry and 1500 °C for the calcination temperature. The glow curve recorded for the most sensitive phosphor was partially erased by photo-bleaching, and thus, should yield optically stimulated luminescence.
