Dy and Ce Co-doped La<SUB>2</SUB>Zr<SUB>2</SUB>O<SUB>7</SUB> Ceramic Powder used for Thermal Barrier Coating

Abstract

Dy and Ce co-doped lanthanum zirconate composite (La_(1.7)Dy_(0.3)(Zr_(0.8)CeZr_(0.2))_2O_7,LDCZ) ceramic powders were prepared by the chemical precipitation method.XRD,SEM,differential Scanning Calorimetry (DSC) and TG,were used to analyze the crystallogrphic phase,microstructure and the phase stability of LDCZ.High-temperature dilatometer,DSC and laser thermal diffusivity methods were used to analyze its thermal expansion coefficient (TEC),specific heat and thermal diffusivity.The results show that the compositions of all prepared ceramic powders are in the range of the synthesis of La_2Zr_2O_7 with pyrochlore structure,the ceramic powders are amorphous mixed oxide at 120℃, the amorphous mixed oxide is converted to composite oxide when temperature is increased to 900℃, and the composite oxide is converted to single La_2Zr_2O_7 with pyrochlore structure at 1200℃.The LDCZ powders keep the pyrochlore structure and there is no phase transformations for LDCZ at high temperatures (～1300℃).The thermophysical results indicate that the thermal expansion coefficient of the LDCZ ceramic is slightly higher than that of conventional Y_2O_3-8wt%ZrO_2 (8YSZ) and the thermal conductivity of the ceramic is 1.28-1.07W/m·K,it is 25% lower than that of La_2Zr_2O_7,which indicates that LDCZ may be an excellent material for preparing thermal barrier coatings.