Effects of nano-sized silicon carbide particulate on microstructure and ionic conductivity for 8 mol % yttria stabilized zirconia based nanocomposites

Strong 8 mol % Y₂O₃ stabilized zirconia (8YSZ)/silicon carbide (SiC) nanocomposites were fabricated by using hot-pressing technique, and effects of dispersed nano-sized SiC particles on microstructure and ionic conductivity of 8YSZ were investigated. Fine SiC particulate inhibited densification and normal/abnormal grain growth of 8YSZ matrix grain due to the decrease of grain boundary diffusivity and mobility. The nanocomposites had fine and homogeneous microstructure, and this phenomenon became more obvious with increasing SiC content. The total conductivity decreased with increasing SiC content due to the decrease in grain boundary conductivity, which should be related to the increase in grain boundary length and the decrease of effective volume of ionic conductor by SiC particles at grain boundaries. For lattice conductivity, the 5 vol % SiC particulate dispersed composite had similar lattice conductivity to the 8YSZ monolith. However, the 20 vol % SiC particulate dispersed composite was found to show higher conductivity than the monolith, which should be attributed to the extension of lattice spacing by the residual stress depends on the thermal expansion mismatch between 8YSZ matrix and SiC particles.