Optical spectroscopy: An effective tool to probe the origin of dielectric loss in Cr doped PrFeO 3

Abstract

The composition dependent dielectric and optical absorption measurements have been carried out on polycrystalline samples of PrFe1-xCrxO3 (x = 0 to 0.20) in order to investigate the possible correlation between (i) dielectric loss; defined in terms of loss tangent (tanδ) (ii) optical band gap (Eg) and (iii) width of electronic disorder i.e. Urbach width (Eu). It has been observed that with increasing Cr doping, the value of tanδ and Eu increases systematically whereas; systematic decrease in Eg has been observed. It appears that the decrease in the value of Eg and increase in value of Eu leads to an increase in the tunnelling probability of electron from valence band to the conduction band which may result in increase in the value of tanδ. Present investigations strongly suggest that there must be a direct correlation between dissipation factor and electronic disorder term i.e. Urbach energy. Here, a completely new way has been established in order to understand the possible correlation between the dielectric loss, band gap and Urbach energy terms in the form of tunnelling probability. Thus, using the combination of dielectric and optical spectroscopy measurements, a new mechanism has been proposed and demonstrated to understand the origin of dielectric loss in highly correlated electron systems in present work. © 2019 Elsevier Ltd and Techna Group S.r.l.