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

[Display omitted] • Low-cost, non-toxic, inorganic brown pigment series ZnFe 2-x Al x O 4 was synthesized. • Octahedral geometry of Fe³⁺ chromophore was distorted after Al³⁺ incorporation. • ZnFe 1.9 Al 0.1 O 4 exhibited high NIR solar reflectance with intense brown colour. • Pigment acrylic coatings demonstrated excellent temperature shielding ability. • Anti-corrosive performance of the pigment was exceptional and consistent over toxic commercial pigments. 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 (ZnFe 1.9 Al 0.1 O 4) 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 ZnFe 2 O 4. The pigment stands out with its promising anticorrosive performance over the commercial toxic candidates, chromates and phosphates, exhibiting excellent R ct = 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. [ABSTRACT FROM AUTHOR]