Effect of preparation techniques on infrared emissivities of Zn0.9Co0.1O powders

Zn0.9Co0.1O powders were prepared by chemical solution deposition, solid-state reaction and sol–gel route at different calcination temperatures. The structure and morphologies of samples were determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The infrared absorption spectra and infrared emissivities in the range of 8–14 μm were investigated by Fourier transform infrared spectroscopy and IR-2 dual-band infrared emissometer. XRD patterns confirmed the hexagonal wurtzite structure of as-synthesized samples but the peaks of the secondary phase, ZnCo2O4, were observed below 1000 °C. Scanning electron micrographs showed large grain sizes of the samples prepared by solid-state reaction and sol–gel processing. The infrared emissivities of samples fabricated by chemical solution deposition and sol–gel route decreased with increasing temperature. Powders obtained using solid-state reaction showed the lowest emissivities, with a minimum value (0.755) at 1150 °C.