International Journal of Engineering and Technology

Radiative rectification is one of the newest solutions for thermal building insulation. It is a phenomenon which has good analogy with electronic diode principle. It consists on being blocking for solar radiations in summer and passing radiations in winter. Among materials which have rectification capacity, Vanadium dioxide (VO2) offers good applicability to building insulation with quite good rectification efficiency. VO2 has a transition temperature around 68°C. Under this temperature, the material has a semiconductor crystallographic structure; therefore it becomes transparent to visible and infrared solar spectra. Above 68°C, the crystallographic structure of VO2 changes to a metallic state for which it becomes more reflective to the same spectra. This semiconductor/metallic transition influences the optical properties of VO2 which are highly dependent to temperature and wavelength. These properties are refractive index n(T,?) and extinction coefficient k(T,?), they are necessary in the optical study of VO2 insulation capacities. Determination of these properties is purely experimental using ellipsometry techniques. In this work we suggest a method for numerical determination of these optical properties. This method uses the Particle Swarm Optimization (PSO) algorithm and it is based on the theoretical model of Lorentz oscillators at VO2 nanoparticles scale. We calculated n(T,?) and k(T,?) for 3 temperatures and compared them with experimental results. This comparison showed good agreement between numerical and experimental results.