Microstructure, thermal shock resistance and thermal emissivity of plasma sprayed LaMAl11O19 (MÂ =Â Mg, Fe) coatings for metallic thermal protection systems

► LaMAl11O19 (M = Mg, Fe) coatings were prepared by air plasma spraying on nickel-base superalloy substrate. ► LaMAl11O19 coatings consist of a hexaaluminate phase with magnetoplumbite structure and an amorphous phase. ► The amorphous phase in coatings disappears and a LaAlO3 phase is formed during thermal cycling at both 1000 and 1200 °C. ► The emissivity of LaFeAl11O19 coating is about 0.7 at short wavelengths and above 0.9 in the wavelength range of 7-14 μm.