Direct correlation between the band gap and dielectric loss in Hf doped BaTiO3
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Effect of Hf doping at Ti site in BaTiO3 on the optical band gap (Eg), Urbach energy (Eu), dielectric constant (ε) and dielectric loss i.e. loss tangent (tanδ) have been investigated. It has been observed that with Hf doping, the value of Eg and Eu systematically increases whereas; the value of dielectric constant and dielectric loss systematically decreases. The decrease in the value of dielectric constant has been explained in terms of reduction in the tetragonality i.e. by c/a ratio. In the present investigation, it has been proposed that increase in the value of Eg and Eu, leads to decrease in the tunneling probability of electron from valence band to the conduction band which may result in decrease in the value of the dielectric loss. Present investigations clearly suggest that the value of dielectric loss is effectively controlled by Eg. Thus, through present studies, a new methodology has been proposed for understanding the origin of dielectric loss. Moreover, a possible correlation between the Eg and tanδ in terms of tunneling probability has been provided.
Authors sincerely thank Dr. Adityanarayan H. Pandey for providing important references and Mr. Devesh Pathak for his help during SEM measurements. SIC IIT Indore is acknowledged for providing experimental facilities. We sincerely thank the Raja Ramanna Center for Advanced Technology (RRCAT) Indore for providing synchrotron radiation facilities. The authors sincerely thank Dr A. K. Sinha, Mr. M. N. Singh and Mr. Anuj Upadhyay for their help during X-ray diffraction measurements. Authors (AK, KW, VM) thank IIT Indore providing financial support through Teaching Assistantship. Ms. Aanchal Sati acknowledges IIT Indore for providing an opportunity to carry out research work through IIT Indore Ph.D. program and CSIR New Delhi for providing Junior Research fellowship through Grant No. 1061651837 for the above said Ph.D. program.
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