Strain-induced partial phase transition in TiO2 nanoparticles manifesting frequency dispersive pseudo-inductive switching of capacitance

Abstract

The appearance of ‘negative capacitance’ (NC) in dielectric spectroscopy not always demonstrates the true reverse charge accumulation between polarizable sites in the associated system. Nonlinear transport of charge-carriers might induce an inductive growth compromising the geometrical capacitance. This sort of dispersion is investigated in mixed phase polycrystalline TiO2 powder having an initial phase ratio of anatase and rutile ~80:20, obtained through mechanical grinding up to 16 h. A significant strain-induced phase transition from anatase to rutile was affirmed from XRD and Raman analysis; whereas reduction in size was nominal. From the Energy Dispersive Analysis of X-rays (EDAX); a remarkable oxygen vacancy formation with longer duration of ball-milling has been observed. In this study, the predominant effects of oxygen vacancy formation on nonlinear hopping conduction-driven inductive response at the higher frequencies are discussed. This genre of frequency-dependent switching can provide an electrical measure of defect-density and traps present in the system. The impacts of strain-induced phase transition on the optical and electrical properties of the material are highlighted in this regard.