Investigation of a new type of composite ceramics for thermal barrier coatings

Abstract

In order to explore a novel material for thermal barrier coatings (TBCs), the composite ceramic materials of lanthanum zirconate (La2Zr2O7) and lanthanum phosphate (LaPO4) were prepared by calcining. The phases and micro-structures of La2Zr2O7/LaPO4 composite ceramic materials were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The properties of La2Zr2O7/LaPO4 material, such as thermal conductivity, coefficient of thermal expansion (CTE) and mechanical properties of La2Zr2O7/LaPO4 were investigated using laser flash method, high-temperature dilatometer and micro-hardness test. Based on XRD patterns, the pyrochlore and monazite phases were obtained in La2Zr2O7/LaPO4 composite ceramic material without any chemical reaction. According to SEM morphology, the La2Zr2O7 was closely near to LaPO4 along with a lot of pores, it might cause the decrease of thermal conductivity. The thermal conductivities of composite ceramics were similar to that of La2Zr2O7. The CTE of them were about 10×10−6K−1, which was close to the value of LaPO4. Because of doping LaPO4, hardness and Young's modulus of samples were lower than that of La2Zr2O7. The studies revealed that the La2Zr2O7/LaPO4 composite ceramics had good mechanical and thermal physical properties and could be applied as new candidate materials for TBCs in the future.