Low-Thermal-Conductivity Rare-Earth Zirconates for Potential Thermal-Barrier-Coating Applications

摘要

Rare-earth zirconates have been identified as a class of low-thermal-conductivity ceramics for possible use in thermal barrier coatings (TBCs) for gas-turbine engine applications. To document and compare the thermal conductivities of important rare-earth zirconates, we have measured the thermal conductivities of the following hot-pressed ceramics: (ⅰ) Gd_2Zr_2O_7 (pyrochlore phase), (ⅱ) Gd_2Zr_2O_7 (fluorite phase), (ⅲ) Gd_(2.58)Zr_(1.57)O_7 (fluorite phase), (ⅳ) Nd_2Zr_2O_7 (pyrochlore phase), and (ⅴ) Sm_2Zr_2O_7 (pyrochlore phase). We have also measured the thermal conductivity of pressureless-sintered 7 wt% yttria-stabilized zirconia (7YSZ)―the commonly used composition in current TBCs. All rare-earth zirconates investigated here showed nearly identical thermal conductivities, all of which were ～30% lower than the thermal conductivity of 7YSZ in the temperature range 25°-700℃. This finding is discussed qualitatively with reference to thermal-conductivity theory.