TWINNING MORPHOLOGIES AND MECHANISMS OF ZNO CRYSTALLITES UNDER HYDROTHERMAL CONDITIONS

Two kinds of twinning morphologies of ZnO crystallites prepared under hydrothermal conditions were obtained. The twirl relations of the crys tallites could be influenced by additives. The twinned crystallites in the pure H2O or weak basic solutions (1 N KOH) are bipyramidal and ta ke (000 (1) over bar) as the twin and composition plane, whereas the t winning morphology of the crystallites obtained from a N KBr or 3 N Na NO2 solutions is dumbbell-like and takes (0001) as the composition pla ne. Various twinning mechanisms based on the linkage of the growth uni ts are suggested. The formation of twin morphologies of ZnO crystallit es clearly demonstrate that twinning of crystals is either a result of differences between symmetrical and energetic most favourable structu re arrangements or due to the consequence of oriented intergrowths.