Dielectric Properties of Pristine and Green-Synthesized Hematite Nanomaterials Vis-À-Vis Their Dependence on Porosity and Particle Size

Abstract

Hematite is obtained using different concentrations of P. tuberosa flower extract. XRD and Raman studies confirm the formation of nanometric size (20–30 nm) and the corundum structure. Particle size depends on the extent of flower extract used for synthesis. Frequency and temperature dependent dielectric constant, dielectric loss, ac/dc conductivity and electric modulus have been explored. Large dielectric constant values (6 × 10³−40 × 10³) at low frequency under room temperature are observed. Dielectric constant (${\epsilon }_r$) depends on frequency, temperature, particle size and porosity. The nature of the frequency dependence of ${\epsilon }_r$ can be explained with the help of the Maxwell-Wagner-Koop's theory. Correlation between particle size and dielectric constant is attributed to significant lattice distortion resulting from reduced grain size. AC conductivity is analyzed with Jonscher's power law, and correlated-barrier-hopping type of conduction mechanism is proposed in these nanomaterials. Temperature dependence of DC conductivity confirms semiconducting behavior of hematite. Investigation into the electric modulus reveals that both electrical conduction and dielectric polarization are governed by a common mechanism. Present study explores into the process of crystal growth influenced by the plant extract and examines its impact on the dielectric property.