Thermo-physical properties of rare-earth hexaaluminates LnMgAl11O19 (Ln: La, Pr, Nd, Sm, Eu and Gd) magnetoplumbite for advanced thermal barrier coatings

Compounds with LnMgAl11O19-type magnetoplumbite structure have been identified as a class of promising competitors to established yttria partially stabilized zirconia (YSZ) as a thermal barrier coating materials on nickel-base alloys due to their excellent thermo-physical properties and relatively low sinterability. In order to achieve better understanding of the structure/property relationships of LnMgAl11O19 (Ln = La, Pr, Nd, Sm, Eu and Gd) magnetoplumbite, the direct influence of gradual variations of constituent upon therma-physical properties was conducted by analyzing the Raman spectrum and X-ray diffraction (XRD) as well as the calculated phonon mean free path. The source of low thermal conductivities was collectively contributed by the strain field fluctuation of the Ln ionic mass and distorted AlO6 octahedron influenced by the interaction with RE3+ ions as well as the intrinsic scattering in the complex crystal cell of LnMgAl11O19 and the highly dense grain boundaries.