Study of microstructure, electronic structure and thermal properties of Al2O3-doped tetragonal YSZ coatings

Abstract Al2O3-doped tetragonal yttria-stabilized zirconia (t-YSZ) coatings were prepared by plasma spraying under various spraying parameters. The analysis of variance reveals that only Al2O3 addition significantly affects thermal properties of coatings. The electronic structures and microstructures results show that the increase in number of defects and boundary density with the increasing addition of Al2O3 enhances phonon scattering resulting in a decrease in the thermal conductivity, which suggests that the Al2O3 addition can improve the insulation performance of the YSZ coating. The increase in boundary density with the increase in Al2O3 addition is due to recrystallization resulting from the decreasing melting point of Al2O3–YSZ composites, lattice distortion, and the presence of amorphous structure and monoclinic Al2O3 pinning at grain boundaries. The change in the coefficient of thermal expansion with Al2O3 addition is attributable to the variation in the bonding strength of the Al2O3-doped t-YSZ caused by the change in lattice constants.