High Temperature Dielectric Response and AC Conductivity Mechanism of (Nd, Ni) codoped BiFeO3

Abstract

BiFeO3(BFO)and Bi0.9Nd0.1Fe0.9Ni0.1O3 (BNFNO) nanocrystalline samples have been synthesized through the sol-gel auto combustion process. Frequency and temperature dependent dielectric measurements have been performed in order to apprehend the influence of (Nd,Ni) co-doping on the conduction mechanism of pristine BFO.Thereal part of the dielectric constant is found to increase with the Nd and Ni doping, which is accredited to higher space charge polarization induced by the dopant ions.The dielectric constant measured as a function of frequency exhibits a dispersivebehaviour within low frequency region and attains a constant value at higher frequencies. A thermally activated relaxation peak is found at around 500K in the BNFNO samplewhich shifts towards lower temperatures at higher frequencies. The AC conductivity follows the Jonscher’s universal dynamic law, which has been utilized to evaluate the value of frequency exponent ‘s’. The decrease in the value of the ‘s’ parameter with the increase in temperature establishes that the conduction mechanism is governed by the correlated barrier hopping (CBH) model. The ac conductivity data has been utilized to evaluate the minimum hopping distance (Rmin) and the binding energies (Wm) of the electrons in BNFNO. Arrhenius equation has been used to fit the experimental data and activation energy has been evaluated at different temperatures. The Activation energy is found to increase with the increase in the temperatures, owing to the creation of more oxygen vacancies instigated by (Nd, Ni) co-doping.