Thermal decomposition of the ammonium zinc acetate citrate precursor for aqueous chemical solution deposition of ZnO

Abstract

The thermal decomposition of an aqueous chemical solution deposition Zn2+-precursor is studied by HT-DRIFT (high temperature diffuse reflectance infrared Fourier transform spectroscopy), on-line coupled TGA-EGA (thermogravimetric analysis - evolved gas analysis by Fourier transform infrared spectroscopy (FTIR) and mass spectrometry (MS)), and HT-XRD (high temperature X-ray diffraction). Using these complementary techniques, it is found that the alpha -hydroxyl group of the citrate ligand plays a significant role in the decomposition pathway of the ammonium zinc acetate citrate precursor. TEM (transmission electron microscopy) shows that crystalline ZnO (zincite) is formed at 390 degreesC, after dehydroxylation of the alpha -hydroxyl group and subsequent decarboxylation of the Zn2+-precursor complex. Before total calcination, ZnO particles are already formed and a residual organic backbone thereby remains. The results obtained by these complementary techniques clearly indicate the importance of thermal analysis in the preparation of ceramics through chemical solution deposition. (C) 2002 Kluwer Academic Publishers.