[ ${alpha}-Al_2O_3$ ] precursor was synthesised by sol-gel method using aluminum sulfate, sodium sulfate and sodium carbonate as law materials. The flaky ${alpha}-Al_2O_3$ crystals were prepared by heating using precursor about $1,050^{circ}C$. In this study, the effect of some transition-metal sulfate ($FeSO_4,;SnSO_4,;ZnSO_4$) addition have been investigated. When iron sulfate was added, it could see that act on impurities in crystal growth process. In case of tin sulfate, distribution of Platelets was very broad. When flaky ${alpha}-Al_2O_3$ crystals were prepared zinc sulfate addition, thickness, size, and distribution of platelets was suited to industrial application. The average diameter of flaky ${alpha}-Al_2O_3$ crystals was about 20 $mu$m, and its thickness was about 0.3 $mu$m. Increasing addition of zinc sulfate, thickness of ${alpha}-Al_2O_3$ platelet was decreased.