Reducing Thermal Conductivity of Ceramic Materials Through Alloying

For gas turbines and advanced nuclear power reactors, ceramic materials are used to provide thermal insulation to metallic components. Reducing the thermal conductivity of these ceramic materials allows further decrease in either metal surface temperature or thickness of the insulating materials. In this paper, our past research on the effects of oxide dopants is summarized with a focus on thermal properties. Metal oxides of different valence, ionic radius, and mass were incorporated into yttria partially stabilized zirconia (7 wt% Y₂O₃-ZrO₂) using mechanical alloying process. The powder blends were consolidated using sintering and plasma spraying. The oxides investigated included trivalent Yb₂O₃, Sc₂O₃ and Cr₂O₃, tetravalent CeO₂ and TiO₂, and pentavalent Nb₂O₅ and Ta₂O5. While all oxides provided improvement to thermal conductivity reduction, the most significant effect on reducing the thermal conductivity of 7YSZ was found by using trivalent oxides. Furthermore, the effect of dopant was also heavily influenced by the molar percentage of dopants.