Inorganic ferrite brown; transformation towards a versatile pigment for energy efficient constructions

Abstract

The present work demonstrates a multifunctional brown inorganic ferrite pigment series, which is free of highly toxic elements, via solid-state ceramic method. Partial replacement of chromophore Fe3+ by Al3+ in the pigment composition (ZnFe1.9Al0.1O4) brought structural distortion in its octahedral geometry that further induced compressive stress inside the crystal unit cell. The introduction of even 5 mol% of Al3+ ions incorporated in place of Fe3+ could able to promote the pigment reflectance profile 25 units higher compared to parent system, particularly with significant colour improvement. Acrylic coating of the pigment on Al substrate was equally well in displaying good colour strength and temperature shielding ability (∼2 °C) with respect to ZnFe2O4. The pigment stands out with its promising anticorrosive performance over the commercial toxic candidates, chromates and phosphates, exhibiting excellent Rct = 4.1 × 109 Ωcm2. The durability of 20 wt% pigment loaded epoxy coating on steel activates through combined action of Zn(OH)2 and FeOOH film mechanism. Since, the pigment exhibits intense colour, high NIR solar reflectance and robust corrosion resistance properties, their use as a high-performance multifunctional pigment is indispensable.