## 3 Results and Discussion  
The morphology, particle size, and phase of synthesized TiO\({}_{2}\) with different calcination temperatures were investigated by transmission electron microscopy (TEM) as shown in Figure 2. It was observed that TiO\({}_{2}\)-300, TiO\({}_{2}\)-600, and TiO\({}_{2}\)-700 showed the mixture of spherical, cubic, and hexagonal shapes while TiO\({}_{2}\)-800 provided an almost hexagonal shape with the agglomeration and aggregation of particles. The particle size of TiO\({}_{2}\)-300, TiO\({}_{2}\)-600, TiO\({}_{2}\)-700, and TiO\({}_{2}\)-800 particles were 8.6 \(\pm\) 1.7, 18.7 \(\pm\) 3.7, 27.6 \(\pm\) 8.2, and 81.6 \(\pm\) 21.6 nm, respectively. It was observed that increasing calcination temperature leads to increasing particle size and crystallite size of TiO\({}_{2}\) particles. At low calcination temperature of 300 \({}^{\circ}\)C, the mixture of anatase (101) and brookite (111) phases with d-spacing of 3.520 and 3.465 nm was observed for TiO\({}_{2}\)-300 (Figure 2a). When increasing calcination temperature to 600 \({}^{\circ}\)C (Figure 2b), there were three phases composed of anatase (101), brookite (111), and rutile (110) with d-spacing of 3.520, 3.465, and 3.247 nm, respectively. TiO\({}_{2}\)-700 (see Figure 2c) showed the mixture of anatase (101) and rutile (200) phases with d-spacing of 3.520 nm and 2.297 nm, respectively. TiO\({}_{2}\)-800 showed only rutile phase (110) with d-spacing of 3.247 nm as shown in Figure 2d. Moreover, inset images in Figure 2 show selected area electron diffraction (SAED) images of TiO\({}_{2}\) particles. The results demonstrated that there was a mixture of anatase (211) and brookite (221) phases observed for TiO\({}_{2}\)-300. When calcination temperature was increased from 300 \({}^{\circ}\)C to 600 \({}^{\circ}\)C, there were three phases composed of anatase (101), rutile (111), and brookite (113) phases. SAED patterns showed anatase (220) and rutile (210) phases for TiO\({}_{2}\)-700 and showed only the rutile (210) phase for TiO\({}_{2}\)-800. Figure 2b-d showed that increasing of calcination temperature from 600 \({}^{\circ}\)C to 800 \({}^{\circ}\)C increased the aggregation of crystallites leading to larger crystallite size and lower surface area since the anatase and brookite phases were completely transformed to the rutile phase. This indicates that crystallite size of TiO\({}_{2}\) powder was increased at high temperature due to larger crystallite size of the rutile phase. It was reported that the most stable crystallite size of anatase and brookite phases is less than 11 nm and 11-35 nm, respectively, while the most stable crystallite size of the rutile phase is larger than 35 nm [32]. In addition, with increasing calcination temperature the crystallinity was increased. This can be attributed to the thermally promoted crystallite growth. Therefore, TEM and SAED images confirmed phase synthesis of TiO\({}_{2}\) powder strongly depend on calcination temperature. At low calcination temperature, anatase and brookite phases were presented. Phase transition of TiO\({}_{2}\) to rutile phase was significant when the calcination temperature was higher. XRD patterns of synthesized TiO\({}_{2}\) particles before and after calcination at different temperatures from 300 \({}^{\circ}\)C to 800 \({}^{\circ}\)C are shown in Figure 3. Anatase phase is the tetragonal structure and consists of the characteristic peaks at 20 = 25.3\({}^{\circ}\), 36.9\({}^{\circ}\), 37.8\({}^{\circ}\), 55.1\({}^{\circ}\), and 70.3\({}^{\circ}\) corresponding to (101), (103), (004), (211), and (220) planes, respectively referenced from the Joint Committee on Powder Diffraction Standard (JCPDS card no. 21-1272).