Research On Preparation And Properties Of Doped-Bi₂Mo₃O₁₂ High Near Infrared Reflective Pigment

Pale yel ow bismuth molybdate with high near-infrared reflectivity was prepared by co-precipitation method.In addition,high-intensity near-infrared reflective pigments with differe nt colors were obtained by doping with different ions（Fe,Ce,Co）.The crystal structure,thermal stability,chemical bond energy,near-infrared reflectance and chromaticity of the sample were characterized by XRD,TG-DSC,XPS,UV-vis-NIR and colorimeter.The effect of calcinat io n temperature,pH value and doping amount on pigment color and reflection performance were discussed.The main findings are as follows:（1）The pale yellowα-Bi₂Mo₃O₁₂ pigment was prepared by using coprecipitation method with bismuth nitrate and ammonium molybdate as raw materials.It was found that the calcination temperature and the pH value of the solution have a great influence on the structure and reflection properties of bismuth molybdate.When the calcination temperature is 600°C and the pH value of the solution is 5,the near-infrared reflectance of the bismuth molybdate sample is as high as 96.67%and the color saturation values is 22.22.（2）Multi-color doped bismuth molybdate pigments with high near-infrared reflect io ns were obtained by doping with different ions（Fe,Ce,Co）.The effects of ion doping on the structure,chromaticity and near-infrared reflectance of the sample were investigated.When the ion doping amount x=0.2,brilliant yel ow Bi_1.8Fe_0.2Mo₃O₁₂ pigment with near-infr ared reflectance of 95.01%,orange-red Bi_1.8Ce_0.2Mo₃O₁₂ pigment with near-infrared reflectance of96.51%and dark gray Bi_1.8Co_0.2Mo3O₁₂ pigment with a near-infrared reflectance of 87.98%were obtained separately.（3）The Fe₂Mo₃O₁₂ phase appears when the concentration of doping concentration x=0.3and 0.4,the chromaticity of the samples remained basically unchanged,and the reflectance of the infrared band of the samples rapidly decreased from 95.01%to 86.31%.The XPS test confirmed the exist of Fe²⁺in the Fe₂Mo₃O₁₂ phase,and the absorption of Fe²⁺in the near-infrared region is the main reason for the decrease of near-infrared reflection performance.（4）The doping of different ions（Fe,Ce,Co）cause the decrease of the band gap of the sample,which leads to the change of the absorption limit in the visible light region of the sample,is the main reason for the change of the chromaticity of the sample.（5）The coating prepared by different ions（Fe,Ce,Co）doped bismuth molybdate inorganic pigment has lower surface temperature than the coating paint prepared by commercia l pigments of similar color in the same direct sunlight.It shows obvious cooling effect of the prepared doped bismuth molybdate inorganic pigment.In conclusion,the doped bismuth molybdate of different colors synthesized by a coprecipitation method have good reflection performance in the near-infrared region,and will be a novel heat-reflecting pigment with potential for application.