Low thermal conductivity Sr2+, Zn2+ and Ti4+ ions co-doped LaMgAl11O19 for potential thermal barrier coating applications

The influences of partial substitution of La3+, Mg2+ and Al3+ by Sr2+, Zn2+ and Ti4+, respectively, in LaMgAl11O19 magnetoplumbite were studied by evaluating the thermal conductivity (κ) and coefficients of thermal expansion (CTE) of La1−xSrxMg1−xZnxAl11−xTixO19 (LSMZATO) solid solutions up to T=1273 K. The X-ray diffraction patterns of LSMZATO (0.0≤x≤0.5) reveal identical magnetoplumbite phase structure. The weakened crystal energy of LSMZATO series results in a maximum value of the CTE at x=0.5. The mechanism behind the lowered thermal conductivity was mainly due to the enhanced phonon scattering by point defects and high-density grain boundary. The lowest κ is ~1.16 W m−1 K−1 at 1073 K, which is due to the phonon mean free path being on the inter-atomic level. The excellent thermo-physical properties qualify Sr2++Zn2++Ti4+ co-doped LaMgAl11O19 magnetoplumbite as promising candidate materials for advanced thermal barrier coatings.