Thermal Property Measurements of YSZ-Al₂O₃ Ceramic Composites

Thermal barrier coatings (TBCs) are used in gas turbine engines to achieve a higher working temperature, and thus lead to a better efficiency. Yttria-stabilized-zirconia (YSZ), a material with low thermal conductivity, is commonly used as the top coat layer to provide the thermal barrier effect. Recent studies demonstrated that YSZ-Al₂O₃ composite layer could reduce the oxygen diffusion through the TBC, thus YSZ-Al₂O₃ composite layer potentially could be used to mitigate the spalling induced failure of a TBC coating. The goal of this study is to investigate the effect of the addition of Al₂O₃ on the thermal properties of YSZ based TBCs. In this study, a stainless steel die was used to make disk shaped samples with 0, 1, 2, 3, 4 and 5 wt% Al₂O₃ /YSZ powder ratios under uniaxial pressure. A laser flash system was used to measure the thermal diffusivity for all samples and the porosity of the samples is measured using mercury porosimetry. It is found that adding Al₂O₃ to YSZ decreases the thermal conductivity and increases the porosity of the ceramic composites.