Effect of alkali metal hydroxide on formation processes of zinc oxide crystallites from aqueous solutions containing Zn(OH)42? ions

Aqueous solutions containing Zn(OH)42− ions were prepared by adding 50 ml of 1.5 mol l−1 aqueous alkali metal hydroxide (MOH: M = Li, Na, K, Cs) to 50 ml of 0.1 mol l−1 aqueous zinc nitrate hydrate (Zn(NO3)2·6H2O). Zinc oxide (ZnO) crystallites were obtained by heating aqueous solutions containing Zn(OH)42− ions at ≥348 or 368 K for 3 h. The morphology depended on both of the heating temperature of the Zn(OH)42− aqueous solution and the alkali metal hydroxide used to obtain Zn(OH)42− ions. According to the result of the kinetics of the zinc oxide formation, it was shown that the decomposition of Zn(OH)42− ions on the zinc oxide surface was the rate determining step when NaOH, KOH and CsOH were used to obtain Zn(OH)42− ions. When LiOH was used to obtain Zn(OH)42− ions, the rate determining step was the nucleation of zinc oxide and/or the adsorption of Zn(OH)42− ions.