Up- and down-conversion cubic zirconia and hafnia nanobelts

Abstract

A direct and scalable approach, based upon a thermal decomposition method under normal atmospheric pressure was introduced, for growing well-defined single-crystalline cubic ZrO2 and HfO2 nanobelts with controllable structural compositions and novel optical properties. A solution of ZrCl4 and YCl3.6H2O in ethanol was first treated with sodium hydroxide to yield a viscous gel mixture. The mixture was transferred into a 15 mL Teflon-lined autoclave and heated at 140°C for 24h. The as-synthesized ZrO2 precursors are composed of Zr(OH) 4 as characterized by Fourier transform IR and thermal analysis. XRD patterns of the YSZ samples obtained with less Y3+ content show a mixture of monoclinic, tetragonal, and cubic phases. The down-conversion emission spectrum that is independent of dopant ions show a peak centered at 470nm, corresponding to band gap emission of the host.