Experimental comparison of the effect of temperature on the vibrational and morphological properties of NixCo3-xO4 nanostructures

This work presents the experimental comparison of the effect of temperature and nickel addition on the synthesis of NixCo3-xO4 nanostructures x = 0.01, 0.04, 0.1, 0.16, using the sol-gel technique with final heat treatment at 600 °C and 800°C. X-ray diffraction (XRD) analysis indicates the formation of pure Co3O4 at 600 °C and the appearance of an additional residual NiO phase at 800 °C. The presence of this phase evidences a deviation in the peaks of the diffraction angle to lower ones generated by the difference in ionic radii, which is related to the insertion of larger ions (Ni2+) doped in the matrix of Co3O4. Scanning electron microscope (SEM) analysis indicates that there is a densification of the grains at higher temperatures, possibly associated with the thermal effect that generates greater interdiffusion. Fourier-transform infrared spectroscopy (FTIR) spectra show two main absorption bands with vibrations Co2+¬O, Co3+¬O and Ni¬O in 456 cm-1. The effect of doping generates a displacement in the bands that are evident in the Raman analysis, where the vibrational mode A1g at 600 °C is translated 28.07 cm-1. The values of SBET specific surface area indicate that as temperature increases, the surface area and volume of micropores decreases