Synthesis and characterisation of Niobium doped Yttria stabilised Zirconia

Abstract

Nb-8YSZ pellets were produced by two different methods – solid state (SS) processing and sol-gel (SG) synthesis, varying the content of Nb for each of them (0 –1.5% Nb). The Nb-8YSZ pellets were sintered at 1550°C, and various characterisation methods were used to obtain the properties. For SS samples, the morphology appear to be increasing in grain size (5 to 8 μm) with addition of Nb, and appears to increase in density. Nb addition also increases monoclinic phase content, and increases conductivity. Excess Nb content will lead to sub-optimal sample properties. The SG samples show different response; grain size decreases (1 to 0.5μm) with increasing Nb content, density, however, increases. Nb addition has a drastic effect on phase content, with no apparent trend. Nb also increases conductivity for SG samples. The difference between method of synthesis (SS and SG) were also studied. SG brings a reduction in phase transformation temperature, increases density and increases conductivity. For both the SS and SG samples, the mol% of Nb that gives the best conductivity value is 1.0 mol%. Also, the best conductivity value is obtained in 1.0 mol% SG sample with 8.013 x 10-6 (Ωcm)-1.