Origin of colossal dielectric behavior in hydrothermally prepared non-stoichiometric α-MnO2 nanorods

Abstract

Abstract Precise incorporation of defects into transition metal oxides is gaining scientific interest among researchers as a pertinent variable for tuning their functional properties. Herein we report an unusual behavior in the dielectric properties of α-MnO2 nanorods prepared by hydrothermal method. Recently, we have reported the origin of ferroelectricity in α-MnO2 nanorods prepared by co-precipitation method which has been ascribed to the co-operative Jahn-Teller (CJT) distortion prevailing in the sample due to defect induced non-stoichiometry. However, ferroelectricity is found to be absent in the hydrothermally prepared sample. Instead the new non-stoichiometry has resulted in the origin of peculiar features like temperature independent dielectric response, very high dielectric constant and low dielectric loss which are the characteristics of colossal dielectric materials. This opens up the prospect of usage of α-MnO2 as a possible candidate for capacitive applications. A thorough investigation into the inter-link between the structural and dielectric properties has disclosed that the novel exotic properties are a result of the non-stoichiometry-triggered interplay between space charges and dipoles within the interior of the nanorods.