  By means of fluctuationnal electrodynamics, we calculate radiative heat flux
between two pla-nar materials respectively made of SiC and SiO2. More
specifically, we focus on a first (direct) situation where one of the two
materials (for example SiC) is at ambient temperature whereas the second
material is at a higher one, then we study a second (reverse) situation where
the material temperatures are inverted. When the two fluxes corresponding to
the two situations are different, the materials are said to exhibit a thermal
rectification, a property with potential applications in thermal regulation.
Rectification variations with temperature and separation distance are here
reported. Calculations are performed using material optical data experimentally
determined by Fourier transform emission spectrometry of heated materials
between ambient temperature (around 300 K) and 1480 K. It is shown that
rectification is much more important in the near-field domain, i.e. at
separation distances smaller than the thermal wavelength. In addition, we see
that the larger is the temperature difference, the larger is rectification.
Large rectification is finally interpreted due to a weakening of the SiC
surface polariton when temperature increases, a weakening which affects much
less SiO2 resonances.
