Light modulation in phase change disordered metamaterial - A smart cermet concept

Abstract

Cermet coatings are popular solar selective absorbers as they allow capturing most of the solar energy while minimising radiative losses. Embedded metallic nanoparticles in dielectric matrices promote multiple internal reflection of light and provide an overall low emissivity. VO2 in the metamaterial state is regarded in this study as a responsive mixed phase comprising metallic rutile VO2 inclusions in semiconducting monoclinic VO2 phase mimicking cermet. The smart cermet responds to thermal stimuli by modulating the size of the metallic inclusions and thereby enabling the manipulation of their interaction with light. The highly reliable and reproducible response of the smart cermet corroborates with the observed ramp reversal memory effect in VO2. We demonstrate a thermally controlled 85% emissivity switch taking advantage of the narrow hysteresis and tuning abilities of the disordered metamaterial.