The mechanism for the colour change of iron chromium black pigments in glazes through transmission electron microscopy techniques

Publication year: 2011
Source: Dyes and Pigments, Volume 91, Issue 2, November 2011, Pages 126-133

Hilmi, Yurdakul , Servet, Turan , Emel, Ozel

Black iron–chromium (Fe–Cr) bearing oxide pigments are generally utilised as effective colourants in a wide variety of applications. However, in the case of their use within ZnO-containing glazes, they yield an undesirable brown colour instead of expected black colour. In order to understand the colour change in this system, we report the use of focused ion beam (FIB) sample preparation technique followed by the use of analytical transmission electron microscopy (TEM) characterisation techniques. According to the results, the formation of a reaction layer between the pigment and glaze was identified with an average composition of Zn0.48Fe0.79Cr1.32O4. Additionally, the valance of…

 Highlights: ► Fe–Cr black pigments lead to an undesirable brown colour in the case of introducing Zn-based glazes. ► Novel microscopy techniques – Focused Ion Beam (FIB) and Analytical TEM – were used to clarify this issue. ► A reaction layer formation composed of multi-grains between the pigment and glaze was identified with an average composition of Zn0.48Fe0.79Cr1.32O4 (atomic %). ► The outward diffusion of Fe into the glaze was observed. ► The valance of Fe ion was 3+ in pigment whilst 2+ in reaction layer and glaze.