Crystal Structure and Optical Properties of CoCr2O4–NiCr2O4 Solid Solutions Prepared by Low-Temperature Combustion Synthesis Method

Abstract

The Co1-xNixCr2O4(x=0.1, 0.2 and 0.3) solid solutions were successfully synthesized by low-temperature combustion synthesis method. The crystal structure and optical properties of the samples were investigated. The samples displayed single phase spinel structure with 30 nm in grain size. Infrared absorption peaks at about 525 and 630 cm-1 corresponded to the vibration of octahedron group ([CrO6] / [NiO6]) and tetrahedron group ([CoO4] / [NiO4]) respectively. Due to the electronic transition of 4A2(F) → 4T1(P) of Co2+, 4A2g → 4T2g of Cr3+, 3T1g(F) → 3T1g(P) and 3A2g(F) → 3T1g(F) of Ni2+, absorption peaks at about 578, 618 and 670 nm were observed in the visible region, making the color center be green. The degree of lightness, greenness and chroma increased, whereas the degree of blueness decreased, making the color of the samples transit from pale green to brilliant green as x value increased.