Apparent crystallite domain size growth in metal oxide nanocrystal ensembles: The importance of surface reactivity of powders for processing

Abstract

A major challenge related to metastable oxide nanoparticles as starting materials for ceramics is to achieve control over their processing related property changes. We compared MgO nanoparticles with those of Ba2+-admixtures exhibiting enhanced surface reactivity. The enhanced surface reactivity promotes particle coarsening and gives rise to a multimodal particle size distribution with a fine fraction of nanocubes (d ​< ​10 ​nm) and a coarse fraction of larger particles. Water adsorption from the ambient has a key influence on sintering and resulting microstructures. After sample exposure to water vapor there arise significant changes in structure and crystallite domain size that originate from size dependent dissolution effects transforming only the fine fraction of particles (<10 ​nm) into hydroxides. Thus, controlled Ba-admixture and segregation at the single particle level provides means to address the impact of surface basicity, hydration and consecutive surface chemistry on microstructure evolution during processing.