Effects of the variation of doping content and heat treatment condition on the dielectric properties of Ga doped α-Fe2O3 system: A promising low loss magnetoelectric-semiconductor

Abstract

The ac conductivity and dielectric properties of the α-Fe2-xGaxO3 samples have been studied in the frequency range 1 Hz–5 MHz and in the temperature range of 203 K–503 K. The samples are electrically semiconductor in nature and the dielectric properties are strongly affected by the transformation of magnetic spin order in the hematite structure. The acconductivity curves exhibited nearly constant loss (NCL) regime at the lower temperatures (where antiferromagnetic spin order dominates) and a charge hoping conduction regime dominates at the higher temperatures (where canted ferromagnetic spin order dominates). The samples showed higher electrical conductivity with the increase of Ga content in hematite structure. The features of electrical conductivity and dielectric properties are strongly dependent on the Ga content in hematite structure and also heat treatment condition of the chemical routed samples. The charge conduction mechanism in the α-Fe2-xGaxO3 system is largely controlled by the correlated barrier hopping of charge carriers, whereas the conduction mechanism in the samples with relatively higher Ga content follows the quantum mechanical tunnelling of charge carriers. The present work carried out a detailed analysis on the temperature and frequency dependent behaviour of the electrical conductivity, impedance spectra, electric modulus, dielectric constant and dielectric loss factor in order to extract the information of the contributions of dielectric parameters from grain and grain boundary of the samples and effect of the heat treatment conditions on dielectric properties.