Comparison of color and optical absorbance properties of divalent ion substituted Cu and Zn aluminate spinel oxides synthesized by combustion method towards pigment application

• Copper spinels exhibit NIR absorbance, zinc spinels exhibit NIR reflectance.
• Color properties retained in spinel oxide + PMMA coating.
• Spinel phases show resistance towards both acid and base.

Present work focussed on the synthesis of inorganic pigments based on spinel oxides of the formula Zn1−xMxAl2O4 (x = 0–0.5, M = Ni, Mn) and Cu1−xMnxAl2O4 (x = 0–0.7). Characterization of the resulting compounds was carried out by Powder X-ray diffraction, Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy. The optical absorption results and color parameters delineate the impact of the host structures viz, inverse and normal spinel: Mn2+ substitution in copper aluminate show a broad absorption band in the NIR region (1000–1800 nm) whereas, the corresponding zinc analogues do not exhibit such absorption. The oxides are found to be highly stable towards acid and base treatment which demonstrates the suitability of the materials for pigment application.

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