Synthesis and structure analysis of aluminum doped zinc oxide powders

Hexagonal Al-doped zinc oxide (ZnO) powders with a nominal composition of Zn_1−x Al _x O (0⩽x⩽0.028) were synthesized by the co-precipitation method. The contents of the Al element in the samples were measured by the inductively coupled plasma-optical emission spectroscopy (ICP-OES) technique. The structures of the Zn_1−x Al _x O (0⩽x⩽0.028) compounds calcined at 1000 and 1200°C have been determined using the Rietveld full-profile analysis method. Rietveld refinements of the diffraction data indicated that the addition of Al initially has a considerably positive effect on the decreasing of the lattice parameters a and c of Zn_1−x Al _x O, but the effect becomes very slight and even negative with the further increase of the Al content. The solid solubility limit of Al in ZnO (mole fraction y) is 2.2l%, resulting in Zn_0.978Al_0.22O. It seems that when the Al content is excessive, Al prefers to form a ZnAl₂O₄ compound with ZnO, but not to incorporate into the ZnO lattice to occupy the Zn²⁺ cites. Two phases, ZnO] (or Al-doped ZnO) and ZnAl₂O₄], are obviously segregated in Zn_1−x Al _x O while the value of x is larger than 0.024. The UV-Vis absorption spectra show that the Al-doped ZnO exhibits a red-shift in the absorption edge without reduced transmission compared with pure ZnO, which also confirms that Al ions enter the ZnO lattice and form a Zn_1−x Al _x O solid solution. Supported by the Chinese 863 Project (Grant No. 2003AA32X230), Guizhou Provincial Governor Foundation (No. 200673), Guizhou Province Technological Breakthroughs Fund (No.20073011) and Guizhou High-Level Talent Foundation (No. TZJF-2007-57)