Effect of Ca addition on near-infrared reflection of SrCuSi4O10

Abstract

Abstract In this study, SrCuSi4O10 powders were synthesized by a complex polymerization method and the effect of Ca addition on the crystal structure and optical properties in the visible and near-infrared regions was examined. Crystalline SrCuSi4O10 was formed at 1,000 °C in air. From the X-ray diffraction measurements, the (002) and (004) reflections of SrCuSi4O10 shifted to higher angles, and the lattice parameter (a and c) decreased with the addition of Ca, suggesting that Ca was successfully introduced into SrCuSi4O10. However, the lattice constant of SrCuSi4O10 increased with further addition of Ca to 10 mol%. Optical measurements of SrCuSi4O10 identified three optical absorption bands in the visible light region, attributed to the d–d transition of Cu2+: namely 2B1g → 2B2g (540 nm), 2B1g → 2Eg (628 nm), and 2B1g → 2A1g (800 nm). The addition of Ca decreased the intensity of these absorptions. The –b* value, which indicates blueness, was estimated using the L*a*b* color system, and SrCuSi4O10 with 5 mol% Ca showed the highest value among the measured samples. On the other hand, the reflectance of SrCuSi4O10 in the near-infrared region increased significantly with the addition of Ca. These results indicate that Ca addition is effective in improving the blue coloration and near-infrared reflectivity of SrCuSi4O10.