Room temperature optical absorption spectroscopy (OAS) and Raman spectroscopy measurements have been carried out in order to understand the effect of structural disorder on the electronic and phononic states. For this purpose, polycrystalline samples of Cr doped PrFeO3 have been prepared via wet chemical route. OAS analysis suggests the systematic scaling of electronic disorder with Cr doping; whereas, shifting in Raman line shapes and an increase in Raman line width has been observed with Cr doping. X-ray diffraction analysis clearly suggests the increase in structural disorders in the form of crystallographic strain with Cr doping, which is consistent with the broadening in Raman line shapes. The major contribution to Raman line width has been understood in terms of temperature independent terms i.e. structural disorder induced by doping. The generation of a new phonon mode at ~510 cm−1 has been observed and understood as a disorder phonon mode due to strain induced structural disorder. Moreover, a systematic correlation between crystallographic strain, Raman line width, disordered parameter (σ) and Urbach energy has been observed, which implies that structural disorder affects phononic as well as electronic states of the system. Such comparative study allows us to find the correlation between densities of tail states, structural disorders and anharmonic effects probed by Raman spectroscopy.

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Temperature-dependent diffuse reflectance spectroscopy (DRS) measurements have been carried out on the polycrystalline sample TiO 2 . Important values from optical parameters such as band gap (E g ), Urbach energy (E U ), and Urbach focus (E 0 ) have been estimated in the range of 300-450 K. In order to understand the experimental value of band gap (E g ) of TiO 2 , i.e., obtained from DRS, a first-principle calculation has been performed. The dependency of E U and the slope of exponential tails (β 1 , β 2 ) of the density of states has also been studied which determines the distribution of exponential tails near the valence and conduction bands in semiconducting oxides. The behavior of optical band gap and E U has also been investigated with the influence of temperature using Cody model. From the temperature dependence of band gap measurements, the value of thermodynamical parameter such as Debye temperature (θ D ) has also been estimated. Thus it appears that the temperature-dependent optical absorption spectroscopy is very powerful and economical tool to probe the electronic structure near band edge and also to estimate the important thermodynamical parameter.

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