In the present study, Co_1-xNi_xCr₂O₄ spinel nanopigment was synthesized by the polyacrylamide gel method. The effects of nickel substitution on morphology, crystal structure, and optical properties were investigated. The powders were characterized using X-ray diffraction, field emission scanning electron microscope, differential thermal analysis, Fourier transform infrared spectroscopy, and ultraviolet-visible spectroscopy. XRD patterns showed characteristic peaks of the spinel structure corresponding to the cobalt chromate phase. The ultraviolet-visible spectrum showed two absorption bands at 613 and 656 nm related to the charge transfer of spin ion Co²⁺ at the tetrahedral position and a change in the absorption spectrum with the increasing nickel content. Besides, TEM results revealed an average particle size of 22 nm for the Co_0.6Ni_0.4Cr₂O₄ sample. CIE-Lab was used to evaluate the color characteristics of the pigments. In this evaluation, L* depicts lightness. The a* and b* parameters are the four colors of human vision include red, green, blue, and yellow. Colorimetric results indicated with the substitution of nickel in the structure of cobalt chromate, its brightness (L^*) increased, a^* became more negative (more green) and b^* tended to be more positive (more yellow).

在本研究中，Co _1-x Ni _x Cr ₂ O ₄尖晶石纳米颜料是通过聚丙烯酰胺凝胶法合成的。研究了镍取代对形态、晶体结构和光学性能的影响。使用X射线衍射、场发射扫描电子显微镜、差热分析、傅里叶变换红外光谱和紫外-可见光谱对粉末进行表征。XRD图谱显示了对应于铬酸钴相的尖晶石结构的特征峰。紫外-可见光谱在 613 和 656 nm 处显示两个吸收带，与自旋离子 Co ²⁺的电荷转移有关在四面体位置和吸收光谱随着镍含量的增加而变化。此外，TEM 结果表明 Co _0.6 Ni _0.4 Cr ₂ O ₄样品的平均粒径为 22 nm 。CIE-Lab 用于评估颜料的颜色特性。在此评估中，L* 表示亮度。a* 和 b* 参数是人类视觉的四种颜色，包括红色、绿色、蓝色和黄色。比色结果表明，随着镍在铬酸钴结构中的取代，其亮度（L ^*）增加，a ^*变得更负（更绿），b ^*趋于更正（更黄）。