Blue nano-pigments of Co_1-xCa_xAl₂O₄ (x = 0.1, 0.2, 0.4, 0.6, and 0.8) were synthesized by the polyacrylamide gel method. The obtained powders were characterized by XRD, SEM, colorimetry and UV-vis. The XRD patterns indicated the characteristic peaks were attributed to the CoAl₂O₄ and CaAl₂O₄ phases with a good crystallinity. The crystallite sizes decreased with the increase of calcium content. The colorimetric data revealed that the increases of blue intensity and bright component originated from the enrichment of calcium. When the content of Co was 0.2 (sample P5), the pigment showed the bluest and brightest color. The UV-vis absorption spectra in the range of 430–670 nm decreased with the increase of calcium content thus causing the pigments became brighter and bluer. Incorporation of calcium elements into the CoAl₂O₄ reduced the production costs and also minimized the damage to the environment. These facts show the potential of the obtained powders for cool coatings.

通过聚丙烯酰胺凝胶法合成了Co _1-x Ca _x Al ₂ O ₄（x = 0.1、0.2、0.4、0.6和0.8）的蓝色纳米颜料。通过XRD，SEM，比色法和UV-vis对所得粉末进行表征。XRD图谱表明特征峰归属于CoAl ₂ O ₄和CaAl ₂ O _4。相具有良好的结晶度。随着钙含量的增加，微晶尺寸减小。比色数据显示蓝色强度和明亮成分的增加源自钙的富集。当Co的含量为0.2（样品P5）时，颜料显示出最蓝色和最亮的颜色。随着钙含量的增加，在430–670 nm范围内的UV-vis吸收光谱下降，从而导致颜料变得更亮和更蓝。将钙元素掺入CoAl ₂ O _4可以降低生产成本，并且还可以最大程度地减少对环境的损害。这些事实表明了所获得的粉末用于冷涂料的潜力。