Molten-salt synthesis of luminescent zirconia nanocrystals

Abstract

Nanocrystals (NCs) of refractory oxides are widely used in both industry and fundamental research, despite their strong covalent bonding posing a serious obstacle to crystallisation under moderate liquid-phase environments. Here, we demonstrate a facile high-liquid-phase synthetic route for the fabrication of a refractory oxide, ZrO 2 , by employing molten metal chloride salt as the liquid reaction medium. The molten-salt-derived ZrO 2 NCs exhibit an average size of approximately 120 nm with a limited size distribution. We also show that the molten-salt process allows for the direct doping of ZrO 2 NCs with rare earth (RE) ions using soluble salt precursors, which results in the strong photoluminescence of the products. These luminescent refractory oxides based on RE-doped ZrO 2 could be promising candidates for high-temperature sensing applications in industry. Furthermore, the molten-salt process could be generalised for the production of refractory metal oxide NCs that are otherwise not easily produced by ordinary wet-chemistry processes.