Open Access Article
This Open Access Article is licensed under a Creative Commons Attribution-Non Commercial 3.0 Unported LicenceSustainable Synthesis of α-Alumina Nanoparticles: Comparative Study of Base-Mediated Crystallization via Co-Precipitation
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Fariha Zannat , Md. Ashraful Alam , Pulak Ghosh , Raton Kumar Bishwas and Shirin Akter Jahan
First published on 30th September 2025
Abstract
Alpha-alumina (α-Al₂O₃) nanoparticles (NPs) were synthesized via a controlled co-precipitation method using three different bases: sodium hydroxide (NaOH), potassium hydroxide (KOH), and ammonium hydroxide (NH₄OH). The influence of each base on the structural, optical, and surface properties of the synthesized nanoparticles was systematically investigated. Characterization techniques, including powder X-ray diffraction (PXRD), dynamic light scattering (DLS), UV-Vis spectroscopy, and zeta potential analysis, were employed. Crystallite size, estimated using multiple models, ranged from 54.67 nm to 94.74 nm, with NH₄OH yielding the smallest size and highest specific surface area (28.36 m²/g). Rietveld refinement confirmed complete α-phase formation for the NaOH and NH₄OH samples, while the KOH-derived sample exhibited minor potassium oxide impurities. UV-Vis analysis revealed a wide band gap (5.4-5.5 eV), and zeta potential measurements indicated enhanced colloidal stability for samples synthesized using NaOH and NH₄OH. Thermogravimetric and differential scanning calorimetry confirmed α-phase development between 1047-1121°C. Transmission electron microscopy revealed spherical morphology and nanoscale particle size. These findings highlight the critical role of base selection in tuning the physicochemical properties of α-alumina and demonstrate the effectiveness of NH₄OH in producing fine, phase-pure, and stable α-Al₂O₃ nanoparticles suitable for applications in high-temperature ceramics, electronics, and photocatalysis.