## 3 Results
### Analysis and Structure of TL Emission from Phosphate Glasses  
As one can find, from the previous data, changing concentration of terbium oxide in phosphate glasses leading to increase of their thermoluminescence yield and also influencing the shapes of TL curves. Because of this, it was necessary to investigate TL mechanism in synthesized glasses. To follow and analyze the impact of terbium dopant and its concentration on TL signal and traps structure, one can apply verified approach based on the mixed experimental methods and computerized deconvolution of the TL curves. The substantial question was the selection of the proper traps distribution model, which should be selected for glow curves deconvolution procedure. Thus, at first one performed T\({}_{\text{max}}\)-T\({}_{\text{stop}}\) measurements for both pure PPG and terbium-doped glass samples irradiated with 10 kGy radiation dose, within the temperature ranges of 50-360 \({}^{\circ}\)C and changing temperature in 2-6 \({}^{\circ}\)C steps. The results obtained from these experiments are presented in Figure 8. From the presented data, one can easily determine the number and nature of traps present in the investigated glasses. For pure PPG glass sample (Figure 8a), the dependence of position of the first maximum present in a glow curve (T\({}_{\text{max}}\)) obtained during reading the sample after irradiation and preheating to T\({}_{\text{stop}}\) temperature vs. T\({}_{\text{stop}}\) revealed the existence of five trapping centers. The first peak represented by a flat line in region of 50-90 \({}^{\circ}\)C was characterized as a single first order kinetics (FOK) signal, next three signals were identified as defects with continuous distribution of energy (straight increasing lines in regions 90-140, 140-190, and 190-310 \({}^{\circ}\)C), whereas the last peak visible as a flat region followed by an increasing tail gave presumption for existence of a single general order kinetics (GOK) peak in the region of 280-360 \({}^{\circ}\)C [48]. Similar analysis of the terbium-doped glass delivered evidence for existence of one FOK peak in the region of 50-90 \({}^{\circ}\)C and five peaks with a continuous trap energy distribution in regions of 90-110, 110-130, 130-160, 160-190, and 190-320 \({}^{\circ}\)C.  
Direct determination of the exact positions of signals contributing to a complex glow curve with strongly overlapping peaks is always a difficult task, so next to the presented \begin{table}
\begin{tabular}{c c c c c} \hline  & **PPG** & **PPG\_Tb01** & **PPG\_Tb05** & **PPG\_Tb30** \\ \hline Slope & \((2.9\pm 0.4)\times 10^{5}\) & \((1.0\pm 0.3)\times 10^{5}\) & \((1.9\pm 0.7)\times 10^{5}\) & \((2.1\pm 0.1)\times 10^{5}\) \\ Pearson’s r & 0.968 & 0.998 & 0.998 & 0.99 \\ \hline \end{tabular}
\end{table} 
Table 4: Parameters of fitted linear functions for glass samples (dose 50–2000 Gy). Figure 8: T\({}_{\text{max}}\)-T\({}_{\text{stop}}\) analysis for pure PPG (**a**) and terbium-doped (**b**) glass samples; irradiation dose 10 kGy per point, heating rate 2 \({}^{\circ}\)C/s. above Tmax-Tstop measurements, one also performed variable heating rate method to facilitate the resolving of the glow curves structure. The method was applied both for pure phosphate glass (PPG) and for terbium-doped samples within the heating rates between 0.5-10 \({}^{\circ}\)C on samples irradiated with 10 kGy radiation dose. Results of these measurements are presented in Figure 9. In case of terbium-doped samples, shutter-reducing light intensity had to be applied. From the VHR measurements, the shifting of TL emission maxima is evident. For PPG sample (cf. Figure 9a), the most prominent peak maximum moves from 98 to 145 \({}^{\circ}\)C, upon changing heating rate from 0.5 to 10 \({}^{\circ}\)C/s. Unfortunately, due to the strong overlapping of peaks, this is the only signal whose position may be unambiguously determined. Nevertheless, the overall shapes of the TL emission curves remain similar, regardless of heating rate applied.