Thermo-optical properties of LaMg1 − xNixAl11O19 (0 ≤ x ≤ 1) hexaaluminates for metallic thermal protection system

LaMg1 − xNixAl11O19 (x = 0, 0.25, 0.5, 0.75, 1) ceramics are fabricated by pressureless-sintering method at 1700 °C for 10 h in air. The microstructure and thermo-optical properties of LaMg1 − xNixAl11O19 ceramics are investigated by the X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy measurements. The influence of NiO doping on structure and thermo-optical properties of LaMg1 − xNixAl11O19 ceramics is investigated. The partial substitution of Ni2+ for Mg2+ results in a significant increase in emissivity at low wavelengths as compared with unmodified LaMgAl11O19. When the Ni2+ content increases to x = 0.75 or above, LaMg1 − xNixAl11O19 ceramics have a high emissivity value above 0.70 at low wavelengths at 500 °C. The measured emissivity of all LaMg1 − xNixAl11O19 ceramics shows a similar trend in the wavelength range of 6 to 14 μm.

Research highlights
► LaMg1 − xNixAl11O19 ceramics were fabricated by pressureless-sintering at 1700 °C.
► LaMg0.25Ni0.75Al11O19 has the highest emissivity value above 0.70 at low wavelengths.
► LaMg1 − xNixAl11O19 ceramics have the similar trend in the emissivity from 6 to 14 μm.