“…However, the applications of iron oxides are not limited to usage in bulk glasses. For instance, the absorption features of FeO and Fe 2 O 3 , make iron oxides useful for spectrally selective coatings for both energy generation [7,9,10], and electrochromic materials for "smart window" applications [11,12]. Due to its high refractive index, n 589 =3.10 [13], Fe 2 O 3 could also be a useful high index material in optical interference filters due its large index excursion relative to SiO 2 , n 589 =1.46 [14].…”