White scheelite-zircon glass ceramic enamels: Clues for their optimization as cool surfaces

Abstract

White enamels were prepared from scheelite and zircon glasses. By modifying the amount of WO3 and ZrO2, different crystalline shapes and percentages were obtained. It was found that the high refractivity of zircon hinders the crystallization of scheelite and thus the mixture of the two glasses lead to non-crystallized regions which in turn influence the glaze optical properties. In these non-crystallized areas the infrared characterization revealed a large amount of non-bridging oxygens leading to an increase of the band-gap energy and a decrease in the both the solar reflectance and whiteness of the enamels. It was concluded that by reducing the percentage of these non-crystalline regions, the scheelite/zircon glass ceramic enamels could be potential candidates for reducing the Urban Heat Island effect.