CONTROLLED MICROSTRUCTURAL PROPERTIES OF ZINC-OXIDE POWDER FORMED BY THE THERMAL-DECOMPOSITION OF ZINC HYDROXYNITRATE

A detailed analysis of the microstructural properties, i. e. , microdistortion, size and shape of crystallite, of zinc oxide produced by thermal decomposition of zinc hydroxynitrate Zn//3(OH)//4(NO//3)//2 is presented. The physico-chemical parameters of the reaction, such as the heating rate, mean decomposition rate, sample mass and residual pressure, are important in determining the microstructure of the ZnO produced. Under the experimental conditions used, the shape of the crystallites is cylindrical on average. By modifying the parameters it is possible to modulate the crystallite sizes and also their anisotropic form factor over a limited range. The influence of the residual pressure is prominent in the formation of reticular microdistortions. Strain-free ZnO, of interest in diffraction line-broadening analysis, can be prepared only in small quantities under vacuum, the upper limit for the precursor mass being about 25 mg.