Infrared radiative properties of plasma sprayed La₂Zr₂O₇thermal barrier coatings

La₂Zr₂O₇(LZO) has emerged as a promising candidate for the next-generation thermal barrier coatings (TBCs) due to its low thermal conductivity and excellent high-temperature stability. While the semi-transparency of LZO to infrared thermal radiation reduces its thermal insulation in high-temperature environments. However, the factors governing the thermal-radiation performance of LZO—namely its refractive index, absorption coefficient and scattering coefficient—are not yet well understood. In this study, we therefore measured the refractive index of LZO across the 1.7–9.0 μm wavelength and analyzed the influence of coating microstructure on its absorption and scattering coefficients. As the porosity increased from 12.2 % to 18.3 %, the average scattering coefficient of LZO coatings at 1–6 μm increases from 1.88 × 10⁴ m⁻¹to 2.15 × 10⁴ m⁻¹. Accounting for porosity-dependent thermal conductivity, the interfacial temperature reduction at the coating-substrate interface reaches 119.3 K with an LZO coating thickness of 400 μm. Furthermore, the porosity of LZO coatings with larger inter-splat pores remains more or less unchanged after 200 h of heat treatment at 1300 °C, and suggests superior sintering resistance.