In this study, an investigation was conducted on the thermal barrier coatings, focusing on their applicability for radiative cooling in the external airframe of the scramjet intake. ZrO2-8 wt% Y2O3 and La2Zr2O7 were plasma sprayed onto Inconel 718 substrate with a bond coat of NiCrAlY. The findings revealed that a maximum emittance of 0.83 ± 0.02 at 973 K was exhibited by Inconel/NiCrAlY/ZrO2-Y2O3 (INY) and maintained good thermal stability up to 1373 K for 2 h in the air. Inconel/NiCrAlY/ZrO2-Y2O3/La2Zr2O7 (INYL) showed a maximum emittance of 0.92 ± 0.02 at 773 K but experienced degradation at higher temperatures. In the thermal exposure temperature range of 298–1373 K, an average emittance of 0.81 ± 0.02 was possessed by INY, while INYL had an average emittance of 0.85 ± 0.05. The thermal stress-induced coating failure and the sintering effect led to the degradation of INYL, while INY exhibited reliable performance while exposed to high temperatures. Computational analysis indicated a reduction of ∼ 230 K wall temperature in the Mach 7 scramjet intake upon using the coatings on Inconel. In summary, the developed plasma spray coatings on Inconel substrate have potential use in scramjet for radiative cooling-based passive thermal management.