Structural, electrical and dielectric properties of ZnFe₂O₄/Cu₂S 3D heterostructures

Abstract

This work reports the fabrication of novel zinc ferrite-copper sulphide (ZnFe2O4/Cu2S) 3D heterostructures and subsequent investigation of the spectroscopic behaviour of various electrical parameters like conductivity, impedance and dielectric loss. The study reveals a non-monotonic behaviour of the real component of impedance (Z'), while the imaginary component of impedance (Z") exhibits a temperature-dependent relaxation frequency, with an estimated activation energy (Ea) of 220.13 meV. The dc conductivity (σdc) measurements reveal the semiconducting nature of the sample and a transition from a ferrimagnetic to a paramagnetic behaviour is reported at the Curie temperature of 327K. In case of ac conductivity (σac), Jonscher's power law σac = Aωn is followed and the exponent n is found to lie in the range 0.679 - 0.735 at different temperatures, which is best fitted into a polynomial of degree six. The temperature variation of n is suggestive of the overlapping large polaron tunnelling (OLPT) model. Further, ac activation energy (Eac) is also calculated, which is found to be smaller than the dc activation energy (Edc), indicating electron hopping between Fe3+ and Fe2+ ions. The numerically computed staying time (τ) of electrons in Fe3+/Fe2+ ionic sites varies with frequency as well as with temperature, ranging from 10-6s to 10-19s. A significant decrease in dielectric loss (tanδ) to the tune of 99% (from 75 at ~100Hz to 0.89 at ~1MHz) is reported at room temperature. In the present scenario, when smart materials like spinel ferrites have garnered significant attention for their promising magnetic and electric properties, our studies of the novel ZnFe2O4/Cu2S 3D heterostructures may provide immense possibilities for tailored applications in various electromagnetic applications.