Effect of Precursor Type on Zinc Oxide Formation and Morphology Development during Hydrothermal Synthesis

Abstract

Semiconducting metal oxide sensors have been widely studied due to their small dimensions, low cost and low power consumption. ZnO is a potential material for gas sensor applications because of its high piezoelectric coefficient, great stability of its hexagonal phase and its pyroelectric property. Hydrothermal synthesis is one of the most useful methods to produce homogeneous, nanosized ZnO powders with high purity, controlled particle size and morphology. The research objectives of this study were to understand formation and growth process of ZnO particles with various morphologies and to investigate role of starting materials, (i.e., zinc chloride (ZnCl2 ) and zinc nitrate hexahydrate (Zn(NO3 ) 2 .6H2O) on the particle morphology. ZnO particles with various morphologies were synthesized via an unstirred hydrothermal method. When using ZnCl2 as a precursor, the final morphology was rod like with a taped tip (length of the rod 0.5-1 µm) after 12 h at 100 °C. On the other hand, final morphology of the produced ZnO particles was branch rod like (5-10 µm) when using Zn(NO3 ) 2 .6H2O as precursor under the same synthesis conditions. Accordingly, a proposed growth mechanism has been suggested.

Semiconducting metal oxide sensors have been widely studied due to their small dimensions, low cost and low power consumption. ZnO is a potential material for gas sensor applications because of its high piezoelectric coefficient, great stability of its hexagonal phase and its pyroelectric property. Hydrothermal synthesis is one of the most useful methods to produce homogeneous, nanosized ZnO powders with high purity, controlled particle size and morphology. The research objectives of this study were to understand formation and growth process of ZnO particles with various morphologies and to investigate role of starting materials, (i.e., zinc chloride (ZnCl2 ) and zinc nitrate hexahydrate (Zn(NO3 ) 2 .6H2O) on the particle morphology. ZnO particles with various morphologies were synthesized via an unstirred hydrothermal method. When using ZnCl2 as a precursor, the final morphology was rod like with a taped tip (length of the rod 0.5-1 µm) after 12 h at 100 °C. On the other hand, final morphology of the produced ZnO particles was branch rod like (5-10 µm) when using Zn(NO3 ) 2 .6H2O as precursor under the same synthesis conditions. Accordingly, a proposed growth mechanism has been suggested.