Low-temperature synthesis of α-Al2O3via endotaxial transformation from sodium meta-aluminate†

Abstract

Alpha alumina (α-Al₂O₃), the thermodynamically stable phase of alumina, is widely valued for its exceptional mechanical, thermal, and chemical properties, making it indispensable in applications ranging from abrasives to advanced ceramics. However, conventional synthesis methods require high calcination temperatures (∼1200 °C), leading to energy-intensive processes, particle coarsening, and agglomeration, which limit the production of ultrafine α-Al₂O₃ powders. To address these challenges, we propose a novel, low-temperature synthesis route for α-Al₂O₃via endotaxial transformation using sodium meta-aluminate (NaAlO₂) as a precursor in the presence of CCl₄ under an Ar atmosphere. Leveraging the structural similarity in Al and O atomic arrangements between NaAlO₂ and α-Al₂O₃, we demonstrate the successful synthesis of pure α-Al₂O₃ at a significantly reduced temperature of 850 °C with a reaction duration of 2 hours and an Ar flow rate of 120 sccm. Systematic investigations reveal that the endotaxial transformation retains the original morphology of the NaAlO₂ precursor, offering a potential pathway to control the size and morphology of α-Al₂O₃. This study not only provides a cost-effective and energy-efficient alternative for α-Al₂O₃ synthesis but also introduces a scalable strategy for producing high-quality α-Al₂O₃ with potential applications in advanced materials and catalysis.