Investigation of Optical Properties of Pentasodium Trioxoundecafluoro‐Trititanate for Optoelectronic Applications

A successful application of the Kubelka–Munk model, modified Kubelka–Munk model and unified methodology for estimating the bandgap in semiconducting materials to the analysis of diffuse reflectance spectra for pentasodium trioxoundecafluoro‐trititanate (Na 5 (Ti 3 O 3 F 11 )) plates grown using a hydrothermal method is reported. The steps involved in interpreting the Kubelka–Munk F ( R ) function and using it for bandgap determination are presented. Bandgap energy ( E g ) calculations are performed after establishing, through an extensive literature review, that (i) values can be obtained by extrapolating a linear fit of the Tauc diagram to zero–using the photon energy axis as the abscissa–for a sample that exhibits negligible absorption of gaps in the sub‐bands, but (ii) if absorption of gaps in the sub‐bands is observed in the Tauc diagram, a linear fit of the Tauc diagram can be performed as in the method described in (i). In addition, another linear line fit is added and used as a new abscissa to replace the photon energy axis used in point (ii). It is established that pentasodium trioxoundecafluoro‐trititanate is a wide‐bandgap material, with bandgap energies of 3.70 eV ( p = 1/2) and 4.0 eV ( p = 2), respectively.