In this paper, we studied the morphology of the cellular interface and cellular structure due to constitutional supercooling in Czochralski-Caxis grown LiNbO3 single crystals which were unintentionally doped with Al impurities.The cellular interface consists of a crowd of trigonal-shaped pyramids and the indices of three pyramidal planes are {0112}, between these pyramids there are solute (Al)-rich grooves. The cellular structure in the grown crystal appears as a bundle of prism-shaped cells parallel to the growth direction [0001] divided by {0112} cell walls relatively rich in solute (Al), or as many forks of three solute-rich {0112} walls. These experimental results establish that the white-stripes, veils and solute trails are the manifestations of cellular structure and that the intermittent cellular structure has originated from the temperature fluctuation. The morphology of cellular interface and cellular structure of oxide materials has been compared with metals and their morphological differences are correlated with their entropy of fusion.