Sol-gel synthesis and properties of europium-strontium copper silicates blue pigments with high near-infrared reflectance

Environmentally benign near-infrared reflective blue pigments Sr1-xEuxCuSi4O10+delta (x ranges from 0 to 0.4) were synthesized via sol-gel method. The pigment samples were characterized by thermogravimetry and differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray diffraction technique, X-ray energy dispersive spectroscopy, scanning electron microscopy, UV-vis-NIR diffuse reflectance spectroscopy and the Commission Internationale de l'Eclairage 1976 L*a*b* colorimetric method. The prepared powders exhibited single-phase tetragonal crystalline structure. The color of the pigments changed from sky-blue to dark blue due to the substitution of Eu for Sr in SrCuSi4O10. With increasing Eu content, the near-infrared solar reflectance increased first and then declined. Adding specific amount of Eu can enhance the near-infrared reflectance and solar reflectance. The prepared pigments presented an optimum near-infrared solar reflectance of 72.31% when the doping content of Eu is 20 mol%. (C) 2016 Elsevier Ltd. All rights reserved.