Synthesis of zinc oxide crystals with different shapes from zincate aqueous solutions stabilized with triethanolamine

ZnO crystals were synthesized from basic aqueous solutions including zincate ions stabilized with triethanolamine (N(C 2 H 4 OH) 3 , teaH 3 ) by heating at 60°C. The influence of the basicity of the solutions on the morphology of the ZnO crystals was examined. The aqueous solutions were prepared using ZnSO 4 ·7H 2 O, N(CH 3 ) 4 OH (TMAOH), and teaH 3 as a zinc source, a base, and a stabilizer, respectively, at a zinc concentration of 0.2 M at a teaH 3 / Zn molar ratio of 4. Clear solutions were obtained at a molar ratio of TMAOH / Zn ≥ 3.0. When the clear solutions, in which glass or polyester substrates were placed, were heated at 60°C, agglomerates of ZnO crystals were deposited on the substrates in the TMAOH / Zn range from 3.0 to 3.6. With increasing the TMAOH / Zn ratio, the shape of the resulting ZnO crystals changed from a short asymmetric column with a hexagonal flat edge and a rounded one, through a rocket‐like shape formed by intergrowth, to a hexagonal rod. Although no films of ZnO were formed, ZnO crystals with different shapes were synthesized. When the glass substrates pre‐coated with a ZnO thin film by a sol‐gel method were used, highly oriented, dense ZnO films were formed. The films consisted of rod‐like crystals aligned normal to the substrate surface. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)