Effect of heat treatment on the optical properties of sol–gel-derived, fully dielectric solar control coatings on glass

Abstract

TiO2 and zeolite were used as high index and low index dielectric materials respectively to generate fully dielectric solar control coatings on glass. TiO2|Zeolite|TiO2 trilayer stacks as well as single layer TiO2 and zeolite coatings were generated on soda lime glass substrates using dip-coating technique. The coatings were densified at 450°C in air using a conventional muffle furnace and a conveyorized belt furnace with a total cycle time of 330 and 30 min, respectively, per layer. The effect of heat-treatment time on the optical properties of multilayered and single-layered coatings was studied. Spectroscopic ellipsometric analysis was carried out on individual layers of the stack to elucidate thickness, roughness, and refractive index data. The ellipsometry data were subsequently used as inputs to simulate the UV–Vis–NIR transmittance spectra of the trilayer stacks generated by TFCalc® software, for comparison with experimentally obtained data. The morphology and phase compositions of the coatings were studied using scanning electron microscopy and grazing angle incidence X-ray diffraction analysis. Different heat treatment schedules were found to result in different optical properties. The results from the present study could be used to recommend suitable heat treatment schedules for generating solar control coatings that could be used for either architectural or automotive applications.