Preparation and Spectroscopy Analysis of Spinel CoCr2.xAlxO4 by Low-temperature Combustion Synthesis

As a member of complex metal oxides, spinel CoCr2O4 has wide application in ceramic pigment, catalysis and magnetic materials. In order to reduce the Cr content and modify the color performance, nanoscaled spinel solid solution CoCr2-xAlxO4(x=0, 0.05, 0.1, 0.2, 0.3 and 0.5) was synthesized by low-temperature combustion synthesis (LCS) method using citric acid (reductant) and metal nitrates (oxidants) as starting materials. XRD, TEM, FT-IR, UV-Vis spectrometer and color spectrometer were employed to characterize the structure, morphology, infrared, ultraviolet-visible curve and the color parameters of the as-prepared sample, respectively. Results show that single-phased and uniform CoCr2-xAlxO4 with about 15-30 nm in size can be prepared by LCS at 800 degrees C. Absorption bands at about 520 cm(-1) 630 cm(-1) and 410-450 cm(-1) in IR curve are corresponding to the vibration of octahedron group and the complex vibration of octahedron and tetrahedron group. Absorption bands at 570, 610 and 660 nm in the visible region of UV-Vis curve are assigned to the (4)A(2)(F)-> T-4(1)(P) of Co2+ and (4)A(2g)-> T-4(2g) of Cr3+. Color spectrometer characterization results indicate that the sample exhibits best color performance with x=0.2, showing a bright bluish green color.