Exploring the Interrelation between Urbach Energy and Dielectric Constant in Hf-Substituted BaTiO3

Abstract

The variation of dielectric constant (ϵr) in the low-frequency region (∼106 Hz) in Hf-substituted BaTiO3 has been modelled considering the electronic disorder in the form of Urbach energy (EU) with the help of a Bohr-like model. Optical absorption spectroscopy has been employed in order to estimate EU and also the band gap (Eg), which are found to scale systematically with Hf incorporation, whereas dielectric measurements reveal a decrease in the value of ϵr observed in the frequency range up to 106 Hz with Hf substitution in these prepared samples. The model predicts EU ∝ 1/ϵr2 and Eg ∝ 1/ϵr2, which agrees with the variation of the corresponding experimental values. Thus, the present work contributes to understanding the interconnection between the optical and dielectric properties of such materials and successfully demonstrates the decrease in dielectric constant with increasing disorder.