Rattler effect caused by size disorder in the cation sublattice of rare-earth zirconates has been proved to be an effective way for the thermal conductivity reduction. Herein, a series of multicomponent ((La1/3Eu1/3Gd1/3)1-xYbx)2Zr2O7 (x = 0, 0.25, 0.5, 0.75 and 1) ceramics were synthesized, their structures and the influence of rattler effect on thermal conductivity were investigated. The increasing Yb3+ doping content causes the phase transformation from pyrochlore structure to fluorite structure. The dual-phase ((La1/3Eu1/3Gd1/3)0.75Yb0.25)2Zr2O7 exhibits enhanced hardness owing to the small grain size of the dual-phase structure, which can effectively alleviate the stress to hinder deformation. Also, it has a higher coefficient of thermal expansion of 11.2 × 10−6/K (1200 °C). Since Yb3+ acts as active resonant scattering center, lower thermal conductivity of ((La1/3Eu1/3Gd1/3)0.75Yb0.25)2Zr2O7 and ((La1/3Eu1/3Gd1/3)0.5Yb0.5)2Zr2O7 caused by rattler effect makes them promising thermal barrier coatings.