Crystal structure and optical properties of CoCr_2O_4-NiCr_2O_4 solid solutions prepared by low-temperature combustion synthesis method

摘要

The Co_(1-x)Ni_xCr_2O_4 (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 run in grain size. Infrared absorption peaks at about 525 and 630 cm~(-1) corresponded to the vibration of octahedron group ([CrO_6] / [NiO_6]) and tetrahedron group ([COO4] / [MO_4]) respectively. Due to the electronic transition of ~4A_2(F) →~4T_1(P) of Co~(2+), ~4A_(2g)→~4T_(2g) of Cr~(3+), ~3T_(1g)(F)→~3T_(1g)(P) and ~3A_(2g)(F)→~3T_(1g)(F) of Ni~(2+), 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.