Phase structure and thermophysical properties of co-doped La2Zr2O7 ceramics for thermal barrier coatings

La2Zr2O7 has high melting point, low thermal conductivity and relatively high thermal expansion which make it suitable for application as high-temperature thermal barrier coatings. Ceramics including La2Zr2O7, (La0.7Yb0.3)(2)(Zr0.7Ce0.3)(2)O-7 and (La0.2Yb0.8)(2)(Zr0.7Ce0.3)(2)O-7 were synthesized by solid state reaction. The effects of co-doping on the phase structure and thermophysical properties of La2Zr2O7 were investigated. The phase structures of these ceramics were identified by X-ray diffraction, showing that the La2Zr2O7 ceramic has a pyrochlore structure while the co-doped ceramics (La0.7Yb0.3)(2)(Zr0.7Ce0.3)(2)O-7 and the (La0.2Yb0.8)(2)(Zr0.7Ce0.3)(2)O-7 exhibit a defect fluorite structure, which is mainly determined by ionic radius ratio r(A(av.)(3+))/r(B-av.(4+)). The measurements for thermal expansion coefficient and thermal conductivity of these ceramics from ambient temperature to 1200 degrees C show that the co-doped ceramics (La0.7Yb0.3)(2)(Zr0.7Ce0.3)(2)O-7 and (La0.2Yb0.8)(2)(Zr0.7Ce0.3)(2)O-7 have a larger thermal expansion coefficient and a lower thermal conductivity than La2Zr2O7, and the (La0.2Yb0.8)(2)(Zr0.7Ce0.3)(2)O-7 shows the more excellent thermophysical properties than (La0.7Yb0.3)(2)(Zr0.7Ce0.3)(2)O-7 due to the increase of Yb2O3 content. (C) 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved.