Thermoluminescence study of aluminum oxide doped with therbium and thulium

In this work, α-Al₂O₃ doped either with Tb³⁺ or Tm³⁺ was prepared by combustion synthesis techniques for thermoluminescent (TL) ionizing radiation dosimetry applications. In this method, the reactants (aluminum nitrate, urea and therbium or thulium nitrate) are ignited in a muffle furnace at temperatures as low as 500 °C. This synthesis route is an alternative technique to the conventional fabrication methods of materials based on α-Al₂O₃ (Czochralsky, Vernuil), where high melting temperatures and reducing atmospheres are required. After combustion, the samples were annealed at temperatures ranging from 1000 to 1400 °C for 4 h in order to obtain the pure α-phase structure and were then irradiated with a Co-60 gamma radiation source. The annealed samples present a well defined TL glow peak with a maximum at approximately 200 °C and linear TL response in the dose range 0.5–5 Gy. It was observed that a 0.1 mol% concentration of Tb³⁺ or Tm³⁺ and annealing at 1400 °C optimize the TL sensitivity. The highest sensitivity was found for Tm³⁺ doped samples which were approximately 25 times more sensitive than Tb³⁺ doped samples. These results strongly suggest that combustion synthesis is a suitable technique to prepare doped aluminum oxide material and that Tm³⁺ doped aluminum oxide is a potential material for TL radiation dosimetry.