Electronic and phononic absorption contributions to near-infrared reflectance of Mg1−xCoxAl2O4, Zn1−xCoxFe2O4 and CrxSbxTi1–2xO2 pigments

Abstract

Mg1−xCoxAl2O4, Zn1−xCoxFe2O4 and CrxSbxTi1–2xO2 pigment series with varying chemical constitution were prepared and structurally confirmed. Valence band maximum extracted from photoemission spectrum and Raman signal area obtained from Raman spectrum were used as representative of electronic and phononic absorption, respectively. Mg1−xCoxAl2O4, Zn1−xCoxFe2O4 exhibit a trivial cooperative behavior of electronic and phononic absorption to the near-infrared reflectance. Nevertheless, CrxSbxTi1–2xO2 established a nontrivial phononic absorption behavior. At low doping regime in CrxSbxTi1–2xO2, electronic absorption dominates the controlling of near-infrared reflectance. Conversely, at high doping regime, the shrinking of phononic absorption play a dominance role to the reflectance. The nontrivial scenario could lead to the understanding of underlying reflective mechanism associated with effects from electronic structure and lattice properties. The results would pave the way for the improvement of solar reflective pigment with compromise of color tuning.