Influence of hydrothermal conditions on the morphology and particle size of zinc oxide powder

Crystalline zinc oxide powder has been successfully prepared by adopting am monia as the base source via the hydrothermal process at temperature greate r than or equal to 100 degrees C. The temperature for synthesizing ZnO powd er is around 200 degrees C lower than that of conventional heating process. The formation and growth ZnO powder under hydrothermal environment progres s rapidly as soon as the temperature reaches 100 degrees C. Prolonging the reaction time at 100 degrees C does not significantly influence the charact eristics of obtained powder; however, raising the reaction temperature slig htly reduces the particle size and the production yield of ZnO powder. On t he other hand, as the pH of the starting solution increases from 9 to 12, t he morphology of ZnO powder markedly varies from an ellipsoidal shape to a rod-like shape. In addition, the crystallinity and particle size of ZnO pow der increase with rise in the pH of solutions, but the yield of production decreases. The reason for the variation of morphology and characteristics o f obtained powder with pH mainly depends on the nucleation states occurring in the hydrothermal reaction. (C) 2000 Elsevier Science Ltd and Techna S.r .l. All rights reserved.