Up- and down-conversion cubic zirconia and hafnia nanobelts

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.