Structural and luminescence properties of pure and Al-doped ZnO nanopowders

Pure and Al doped zinc oxide nanopowders have been synthesized by sol–gel route. This is a simple and inexpensive method permitting to obtain a very small grain size powders. Zinc acetate dehydrate was first dissolved in a mixture of 2-methoxyethanol and mono-ethanolamine (MEA) solution, were used as a solvent and stabilizer respectively and doped with a quantity of aluminum nitrate, varying from 0 to 10 mol%. The obtained gel is then calcinated in air at 500 °C. The samples are characterized by XRD, SEM and photoluminescence (PL) studies. The XRD results indicate that pure and Al-doped ZnO powders are solid solutions crystallizing in pure würtzite structure, and consisted of a mixture of nanoparticles with grain size between 23 and 36 nm. The grain size decreases strongly with increasing Al concentration and reaches its lowest value at 5 mol% Al. The PL spectra show that the most important establishment is that the powders show luminescence peaks from green to ultraviolet light, and thus can be used to manufacture transmitters using these emissions. The peaks connected to the blue luminescence are the most intense, and they are generated by transitions involving (Zni). The SEM images show a formation of pebbles with sizes decreasing with Al concentration and a morphology evaluating, qualitatively, from pebbles without cavities to highly porous ones.

► The powders follow the würtzite structure and possess a very small size.
► The grain size deceases as a function of Al concentration.
► The powders’ morphology evaluates with increasing Al concentration from pebbles without cavities to highly porous powder.
► The blue luminescence peaks of the PL spectrum covering the green to the ultraviolet area are the most intense.
► The violet luminescence intensity decreases with increasing Al concentration.