The ultra-low glasslike thermal conductivities of Y3+- and Ce4+- codoped lanthanum zirconate pyrochlores for potential thermal barrier coating applications

It is urgent to develop thermal barrier coating (TBC) topcoat materials with ultra-low thermal conductivities for next-generation gas turbine engines. A novel pyrochlore-based single-phased ceramic, tuned by codoping of lanthanum zirconate, (La 1-x Y x ) 2 (Zr 1-y Ce y ) 2 O 7 , has been synthesized from the solid state reaction method. The thermal conductivity of (La 1-x Y x ) 2 (Zr 1-y Ce y ) 2 O 7 not only exhibits a temperature-independent trend but also reaches as low as 0.93 W·m −1 ·K −1 , a value that is lowest of fully dense crystalline solids in open literature, attributing to the following two combined effects. The first is the strong scattering of phonons by small-sized Y 3+ cations occupying the oversized atomic cages formed by the distinctive pyrochlore structure. The second is the lattice softening effects arising from larger-sized Ce 4+ substituting Zr 4+ cations. The above two effects act in concert and thus form a glasslike and ultra-low thermal conductivity of (La 1-x Y x ) 2 (Zr 1-y Ce y ) 2 O 7 solid solutions, which is ideal for next-generation TBC topcoat applications.