Coupled Multivariable Synthesis of Uniform, Monodisperse, and Multi‐Scale Spherical Precursors and α‐Al ₂ O ₃ Powders

ABSTRACT Preparing spherical α‐Al 2 O 3 powders with consistent particle size, morphology, and dispersion is challenging. To address this issue, this study proposed a multi‐variable synergistic regulation approach. The study explored how three key variables—Al 3 + concentration, SO 4 2 − /NO 3 − ratio, and urea content—interacted and influenced precursor particle size, morphology, and dispersion during hydrothermal synthesis. The results showed that a higher SO 4 2 − ratio increased particle size but also caused agglomeration, while a higher NO 3 − ratio favored the formation of fine, well‐monodisperse spherical particles. A higher Al 3 + concentration promoted particle growth and increased particle size, but required the right anionic environment to prevent agglomeration. Urea showed threshold behavior, strongly influenced by the anionic environment and Al 3 + concentration. By optimizing these variables synergistically, we successfully synthesized spherical precursors with uniform particle size, consistent morphology, and high monodispersity across the nanometer to micrometer scale. After calcination, they were completely converted to α‐Al 2 O 3 with no change in morphology.