Sol-gel processing of yttria-stabilized zirconia films derived from the zirconium n-butoxide-acetic acid-nitric acid-water-isopropanol system

A stable yttria-stabilized zirconia (YSZ) sol has been synthesized by the controlled hydrolysis of zirconium n-butoxide. Acetic acid and nitric acid were used as chelating agent and catalyst, respectively. The addition of acetic acid and increasing the amount of nitric acids to the system significantly enhanced the sol stability. The viscosity of YSZ sol with the concentration less than 0.80 mol/l was independent on the shear rate, whereas those with the concentration over 1.2 mol/l showed shear-thinning behavior. The reduced viscosity of YSZ sol had linear relationship with sol concentration. These rheological behaviors are attributed to the polymeric nature of YSZ sol. XRD diffractograms of calcined YSZ xerogel confirmed that fully stabilized cubic zirconia phase was formed at a temperature as low as 600°C. Spin coating of YSZ sol on Si substrate followed by heat treatment at 600°C for 2 h in air produced uniform crack-free YSZ films of 70-135 nm thickness.