  A thermal diode transports heat mainly in one preferential direction rather
than in the opposite direction. This behavior is generally due to the
non-linear dependence of certain physical properties with respect to the
temperature. Here we introduce a radiative thermal diode which rectifies heat
transport thanks to the phase transitions of materials. Rectification
coefficients greater than 70% and up to 90% are shown, even for small
temperature differences. This result could have important applications in the
development of futur contactless thermal circuits or in the conception of
radiative coatings for thermal management.
