**3.8 Thermoluminescence study of pure Gd2O3 phosphor**

The TL response of the Gd2O3 phosphor was recorded under 254 nm UV exposure and 60Co gamma exposure for the phosphors prepared by both urea and glycine fuel. The TL glow curve of phosphors prepared with both the fuels was recorded under 254 nm UV exposure immediately after 5 min exposure time at 6 Cs<sup>−</sup><sup>1</sup> heating rate. For the combustion synthesized phosphor, the TL glow peak was found at 103°C and 111°C for urea and glycine fuels, respectively. For 1 kGy gamma exposure at 6 Cs<sup>−</sup><sup>1</sup> heating rate, the TL glow peak was found at 232°C and 221°C (**Figure 11**) for urea and glycine fueled phosphors, respectively [10].

Chen's peak shape method was used to determine all the kinetic parameters including order of kinetic, activation energy, shape factor, and so on [4–6, 11] (**Table 1**). The activation energy for TL glow curve for combustion synthesized both phosphors has 0.66 eV for UV exposure and 0.71 and 0.72 eV for gamma exposure. Due to gamma exposure, deeper traps were formed, which are responsible for the higher activation energy value. The phosphor follows second-order kinetics as the obtained shape factor value for UV exposure and gamma exposure was in the range of 0.49–0.52 and 0.50–0.54, respectively, which is near to 0.52 for second-order kinetics (**Table 2**).

### **Figure 11.**

*TL glow curve for 6 Cs<sup>−</sup><sup>1</sup> heating rate and 10 min UV exposure with (A) urea fuel and (B) glycerin fuel. TL glow curve for 6°Cs<sup>−</sup><sup>1</sup> heating rate and 1 kGy gamma exposure (C) urea fuel and (D) glycerin fuel (Reproduced from [8]).*


### **Table 1.**

*X, Y coordinates for CIE diagram for Gd2O3 phosphor.*


### **Table 2.**

*Trapping parameters for optimized TL glow curve.*
