Low-infrared-emissivity atmospheric plasma-sprayed LaBaCo2O5 + perovskite coatings toward passive infrared stealth

Atmospheric plasma-sprayed (APS) ceramic coatings are widely used for infrared stealth applications, yet low emissivity achieved in bulk materials is often difficult to retain after spraying. Here, Ca-doped La 1 – x Ca x BaCo 2 O 5 + δ perovskite is employed as a representative system to investigate infrared emissivity control from bulk ceramics to APS coatings under realistic manufacturing conditions. Ca substitution enables effective tuning of bulk electrical transport and infrared emissivity, establishing a low-emissivity baseline in dense ceramics. Using the bulk ceramics as an internal reference, the influence of spray power on coating morphology, lamellar defects, and infrared emissivity is systematically examined. The APS coatings exhibit engineering-relevant low emissivity, reaching ∼0.12–0.15 in the 3–5 μm band and ∼0.20 in the 8–14 μm band after surface polishing, achieved with a simple single-layer coating configuration. Infrared thermal imaging under identical actual temperatures confirms passive infrared signature suppression, where the apparent temperature contrast originates from emissivity differences rather than real thermal variation. The results demonstrate that while Ca-enabled bulk compositional tuning defines a low-emissivity baseline, coating-level emissivity is fundamentally constrained by spray-imprinted lamellar microstructures. This work provides coating-level insight directly relevant to the engineering of infrared-stealth ceramic coatings fabricated by APS.