Sol-Gel ceramic glazes with photocatalytic activity

A frit is a glassy ceramic composition that has been fused, quenched, and granulated. A single frit or a mixture of frits and ceramic materials forms a ceramic glaze. The purpose of this pre-fusion is to render any soluble and/or toxic components insoluble by rendering it inert in a glassy composition with silica and other added oxides. The ceramic glaze dispersed in water (ceramic slip) is deposited on a ceramic body and fired for waterproofing and aesthetic purposes. Multicomponent frits (zinc-potassium borosilicate system) with similar behavior to conventional ceramic frits for single-firing ceramic glazes (“monoporosa” glazes fired at 1080 °C) were prepared by Sol-Gel methods (monophasic and polyphasic gels) avoiding the pre-fusion and characterized as photocatalytic agents (showing high degradation activity on Orange II). The effect of doping with bandgap modifiers (V 2 O 5 , Sb 2 O 5 and SnO 2 ) and also with devitrification agents (ZrO 2 to crystallize zircon, Al 2 O 3 to anorthite, Mo 2 O 3 to powellite and ZnO to gahnite ZnAl 2 O 4 ) were analyzed. Multicomponent frits (zinc-potassium borosilicate system) with similar behavior to conventional ceramic frits for single-firing glazes (1080 °C) prepared by Sol-Gel methods (monophasic and polyphasic gels), without pre-fusion, shows photocatalytic activity. Highlights Multicomponent frits (zinc-potassium borosilicate system) with similar behavior to conventional ceramic frits were prepared by Sol-Gel methods without pre-fusion. Zinc and potassium borosilicate-based glaze, modified with alumina and calcium, is considered the optimum for conventional applications, and shows a moderate photoactivity with a half-life period of 77 min. Doping with bandgap modifiers enhances the photoactivity; V 2 O 5 or SnO 2 show good photoactivity in the 5 w% sample (t 1/2 = 55 and 58 min, respectively). Doping with devitrification agents (ZrO 2 to crystallize zircon, Al 2 O 3 to anorthite, Mo 2 O 3 to powellite and ZnO to gahnite ZnAl 2 O 4 ) shows that the photocatalytic activity is low, similar or lower than the SG4 zinc-potassium borosilicate parent glaze.