In the synthesis prepared by sol-gel technique with EDTA, Al(NO₃)₃·9H₂O and LiNO₃ as starting materials. Table 1 shows chemicals used in synthesis process. Procedure of synthesized γ-LiAlO₂ powder by sol-gel with EDTA method as shown in Figure 1. Firstly, 0.5 M LiNO₃ and 0.5 M Al(NO₃)₃ × 9H₂O were separately dissolved in deionized water. The solution was heated to 70˚C and stirred

during 1 h. Secondly, 0.5 M citric acid and 1 M EDTA were separately dissolved in ammonium hydroxide. NH₄OH solution was added to adjust pH = 9. Thirdly, these two solutions were mixed together and heated to 90˚C. A viscous gel was obtained after water evaporation. Then the viscous gel was transferred to a ceramic bowl and was heated to 200˚C on hot plate to remove organic compounds. The gel burns itself on a hot plate and a dark grey powder was obtained. The product was then calcined for 4 h in airflow at 600˚C, 800˚C, 900˚C and 1000˚C.

Characterization of the material was examined by Scanning Electron Microscopy (SEM, The S-4800 (FESEM HITACHI, Japan). The XRD is used to confirm the crystalline nature of the synthesized LiAlO₂ material. The XRD machine is equipped with diffraction software with Cu-K_α radiation and scanning angle from 10˚ to 70˚ at room temperature. Phase of the material was analyzed by XRD: D8 Advanced–Bruker, Germany Cu/Kα₁. In addition, the synthesized γ-LiAlO₂ powder was irradiated at dose range from 2 Gy to 30 Gy to evaluate the TL response and linearity. The TL glow curves were examined using a Harshaw 4000 TLD reader. The TL measurement was carried out at temperature range from 50˚C to 400˚C with a constant heating rate of 10˚C/s.

The surface morphology of the synthesized material was investigated by SEM technique. SEM images of the powders calcined at different temperatures 600˚C, 800˚C, 900˚C and 1000˚C for 4 h are shown in Figure 2. According to the results obtained from Figure 2, the size of the synthesized particles was determined as a few µm. The gain size tends to be larger and denser when increasing calcination temperature.

In order to determine the percentage of reactions and crystal structures of synthesized lithium aluminate, X-ray diffractograms of the material are given in Figure 3.

This figure illustrates the XRD patterns of the phase change of the synthesized product depending on calcination temperature. According to plot (a) of Figure 3, it was 8% to Li₂CO₃, 11% to LiAl₅O₈ and around 81% to γ-LiAlO₂ at calcination temperature 600˚C. When increasing calcination temperature at 800˚C, it was 14% to LiAl₅O₈ and around 86% to γ-LiAlO₂ and disappeared Li₂CO₃ as shown in plot (b) of Figure 3. In conclusion, a complete transformation to γ-LiAlO₂ was not achieved.

The pure γ-LiAlO₂ phase is obtained at temperature 900˚C and 1000˚C are presented in plots (c) and (d) of Figure 3. In conclusion, a complete transformation to γ-LiAlO₂ was achieved at temperature higher than 900˚C. Synthesis reactions were realized as shown in following equations:

LiNO 3 + Al ( NO 3 ) 3 × 9H 2 O + EDTA + C 6 H 8 O 7

→ 600 ˚ C LiAl 5 O 8 + Li 2 CO 3 + γ -LiAlO 2

→ 800 ˚ C LiAl 5 O 8 + γ -LiAlO 2

→ > 900 ˚ C γ -LiAlO 2

Figure 4 illustrates the Thermoluminescence glow curves of synthesized γ-LiAlO₂ powder that were irradiated with different irradiation doses at a constant heating rate of 10˚C/s. This figure also shows that there is one peak around 150˚C and another peak near 271˚C. Thermoluminescence glow curves were registered in the range from 50˚C to 400˚C. This figure also shows that the TL intensity increases as the irradiated dose increases.

To check the linearity, the product was irradiated with different doses from 2 to 30 Gy. The glow curves were recorded on Harshaw 4000 TL reader. The linearity is well observed in the full range of irradiated doses as shown in Figure 5. The linearity is observed in the synthesized γ-LiAlO₂ material with regression coefficient (R²) is 0.9971.

For studying the fading effect samples were irradiated to a dose of 15 Gy and TL readouts were taken at regular intervals of time. The material has less than 8% after 20 days of storage.

In order to check the reproducibility of material with same sensitivity, a batch of 10 samples each of 5 g weight was prepared. Variation in the thermoluminescence intensity of sample in the batch was found to be around ±3%.

The effect of heating rate on the sample has been studied by heating the sample at different heating rates. Not much loss in TL intensity was observed at different heating rates. However, the main glow peak shifts from 225˚C to 271˚C at heating rate 2˚C and 10˚C/s, respectively.