To enhance the insulating properties of a thermal barrier coating, one has to focus on new materials with lower intrinsic thermal conductivity than established yttria-stabilized zirconia. Substances with pyrochlore structure were investigated. Starting from lanthanum zirconate, substitutions of the lanthanum by other trivalent rare-earth elements were made, and the thermal conductivity and the thermal expansion coefficient of the manufactured materials were measured. A complete substitution of the lanthanum led to increased thermal expansion coefficients, whereas the partial substitution did not show an appreciable effect. The thermal conductivities of the modified materials were lower than that of the pure lanthanum zirconate for temperatures <1000°C for all amounts and elements of substitution. A comparison of the observed values with calculated values of the thermal conductivities showed a relatively good agreement.N. Padture-contributing editor Manuscript No. 186991.
Advanced ceramic materials of perovskite structure have been developed for potential application in thermal barrier coating systems, in an effort to improve the properties of the pre-existing ones like yttriastabilized zirconia. Yb 2 O 3 and Gd 2 O 3 doped strontium zirconate (SrZrO 3 ) and barium magnesium tantalate (Ba(Mg 1/3 Ta 2/3 )O 3 ) of the ABO 3 and complex A(B 0 1/3 B 00 2/3 )O 3 systems, respectively, have been synthesized using ball milling prior to solid state sintering. Thermal and mechanical investigations show desirable properties for high-temperature coating applications. On atmospheric plasma spraying, the newly developed thermal barrier coatings reveal promising thermal cycle lifetime up to 1350°C.
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