Al2O3/yttrium compound core–shell structure formation with burst nucleation: a process driven by electrostatic attraction and high surface energy

Abstract

A partial wet chemical route has been developed, in which aluminium oxide (Al₂O₃) nanoparticles in a Y(NO₃)₃ solution are induced to form a core–shell-structured yttrium aluminum garnet (YAG) precursor based on a burst nucleation synthesis. By simulating the reaction conditions with urea and ammonium bicarbonate as precipitants, a two-step mechanism involving different dynamic processes is proposed to describe the core–shell structure formation. During the majority of the process, the electrostatic attraction between the opposite surface charges of Al₂O₃ and nanoparticles of the Y-compound is regarded as the single driving force. However, the high surface energy of Y-compound nanoparticles originating from the burst nucleation process plays a key role in completing the formation of the core–shell structure. The precursor obtained can be transformed into pure YAG nanoparticles, which retain the morphology of the Al₂O₃ template, and these are of sufficiently high quality for the preparation of transparent ceramics. An understanding of the mechanism makes this a novel method for the synthesis of the nanostructured core–shell binary oxide precursor.