Robust window for infrared energy

An article comprising:

• a composite substrate comprising a matrix material and particles of a nano-dispersoid dispersed within the matrix material, wherein the particles of the nano-dispersoid are less than about 100 nm in at least one dimension;
• and
• a composite coating disposed over the substrate and extending from an interface with the substrate to an external surface, the composite coating comprising a first phase and a second phase, the second phase having a higher resistance to erosive wear than the first phase;
• wherein the coating comprises a compositional gradient proceeding from a first composition at the interface of the coating with the substrate to a second composition at the external surface, the first composition comprising a higher concentration of the first phase than that of the second composition;
• wherein the first phase comprises a material selected from the group consisting of magnesium aluminate spinel, yttrium aluminate garnet, cubic zirconium oxide, yttrium oxide, magnesium oxide, alpha aluminum oxide, aluminum oxynitride, and rare earth oxides;
• wherein the second phase comprises a material selected from the group consisting of cubic boron nitride, silicon carbide, silicon nitride, diamond-like carbon, diamond, and boron phosphide;
• wherein the coating and substrate together cause scattering of up to about 5 percent of incident infrared radiation.