Tailoring Al-Doped ZnO Nanoparticles via Conventional and Microwave Hydrothermal Methods

Zinc oxide (ZnO) nanoparticles are promising materials for optoelectronic applications due to their multifunctionality and wide band gap. However, their low electrical conductivity limits broader use. Aliovalent doping with trivalent cations, especially Al³⁺, has been employed to enhance electrical and optical properties by increasing free carrier concentration. In this study, Al-doped ZnO (AZO) nanoparticles were synthesized via hydrothermal methods using both conventional and microwave-assisted heating. Structural and spectroscopic characterizations were performed using XRD, FTIR, Raman, and diffuse reflectance spectroscopy. Results confirmed successful Al incorporation and highlighted the effect of the heating method on particle size, crystallinity, and defect concentration. Microwave-assisted synthesis led to smaller and more uniform particles, while conventional heating produced larger polycrystalline structures. Band gap values ranged from 3.28 to 3.43 eV and were influenced by Al content and microstructure. This work presents a simple, scalable approach for synthesizing AZO nanoparticles with tunable properties, suitable for transparent conducting oxide (TCO) applications.