At high temperature, thermal radiation accounts for a large part of the heat transfer. Therefore, the ability to tune thermal emission is paramount to improve energy efficiency when heating and cooling. It is also one of the keys for converting efficiently heat into electricity in a thermophotovoltaic system.

Electromagnetic properties of natural materials are mainly determined by their chemical composition. The metamaterial approach provides additional degrees of freedom for tailoring these properties by playing on the internal structure. This accrued flexibility is of particular interest for the design of thermal emitters: it allows full spectral control and impedance matching with free space, thereby maximizing the emission for a chosen wavelength range.

Unfortunately, most existing metamaterials rely on metals with a low melting point such as gold or silver. So far, the attempts to realize refractory metamaterial emitters relied either on refractory metals (e.g. Ta, Mo, W) or on nitrides (e.g. TiN, AlN, ZrN). These materials do have high melting points but are prone to oxidation which limits their operating temperature in air.

In this presentation, we will show how using innovative fabrication approaches and making the proper choice for associating a conducting and a dielectric material allows elaborating refractory metamaterials with tunable emissivity in the near infrared (NIR) that can operate in air at temperatures exceeding 1000°C.