Spectrally selective surfaces of Ni-pigmented anodic Al2O3

Abstract

Ni pigmentation of anodic Al₂O₃ is obtained by electrolytic coloration. Durable coatings with good spectral selectivity (a/e≃8) are produced. Scanning electron microscopy, Auger depth profiling, and atomic absorption analysis lead to the formulation of a detailed structural model, its most essential feature being a thin layer comprising a mixture of Ni and Al₂O₃ located near the bottom of the anodic film. Experimental spectral reflectance data agree well with computer calculations, provided the optical properties of the metal‐insulator layer are described with the Bruggeman effective medium theory.