Thermal conductivity of (Sm 1– xLa x) 2Zr 2O 7 ( x=0, 0.25, 0.5, 0.75 and 1) oxides for advanced thermal barrier coatings

Abstract

Pyrochlore oxides of general compositions, A 2Zr 2O 7, where A is a 3+ cation (La to Lu), are promising candidate materials for applications as high temperature thermal barrier coatings because of their high melting points, high thermal expansion coefficients, and low thermal conductivities. In this study, oxides of Sm 2Zr 2O 7, (Sm 0.75La 0.25) 2Zr 2O 7, (Sm 0,5 La 0.5) 2 Zr 2O 7, (Sm 0.25La 0.75) 2Zr 2O 7 and La 2Zr 2O 7 were prepared by solid reactions at 1600 °C for 10 h using Sm 2O 3, La 2O 3 and ZrO 2 as the reactants. The phase compositions of these ceramic materials were analyzed by X-ray diffractometer (XRD) and fourier transform infrared spectroscopy (FT-IR) methods, respectively. The microstructure was observed by scanning electronl microscope (SEM). The thermal conductivities of these ceramic materials were measured using laser-flash method. XRD and FT-IR results showed that pure ceramic materials with pyrochlore structure were prepared successfully. SEM results indicated that microstructures of these ceramic materials were dense and grain boundaries were very clean. The La 2O 3 doped Sm 2Zr 2O 7 pyrochlores (Sm 0.75 La 0.25) 2Zr 2O 7 and (Sm 0.5 La 0.5) 2 Zr 2O 7 had lower thermal conductivity than the undoped Sm 2Zr 2O 7. The thermal conductivity of (Sm 0.25La 0.75) 2Zr 2O 7 was found to be lower than that of La 2Zr 2O 7. The results showed that these ceramic materials had the potential to be used as candidate materials for TBCs.