Figs. 2 and 3 show XRD patterns of as synthesized Al2O3 powders from different conditions after calcination at 1100 C and
1000 C, respectively. As shown in Fig. 2a–d, only a-Al2O3 diffraction peaks were observed at 1100 C, While, From the
Fig. 2b and e, when polyvinylpyrrolidone was added without glucose in the process, a-Al2O3 was observed along with u-Al2O3. Which indicating that the addictive of glucose promoted the transformation of a-Al2O3. As shown in Fig. 3, small amounts of g-Al2O3 were observed in Fig. 3a, b and d. From Fig. 3c, e and f. we can find that the powder can be transformed into a single phase from Al-4,Al-7 and Al-8 at a relatively low temperature of 1000 C. Indicating that there was no benefit of polyvinlpyrrolidone on lowering the phase transformation temperature of a-Al2O3. With the increasing amount of seed particles, the intensity of g-Al2O3 diffraction peak became weaker, when the amount of seed was more than 3.5%, the pure a-Al2O3 can be obtained after calcination at 1000 C for 2 h