Variable range hopping transport and dielectric relaxation mechanism in GdCrO3 rare-earth orthochromite perovskite

The polycrystalline GdCrO3 (GCO) perovskite orthochromite was synthesized by the sol–gel auto-combustion method. The Rietveld refined X-ray diffraction (XRD) profile of GCO confirms that the orthorhombic phase crystallizes in perovskite crystal structure with space group Pbnm. The transmission electron microscopy and selected area electron diffraction divulge the polycrystalline nature of the perovskite chromite. The field emission scanning electron microscopy (FESEM) images reveal the microstructural polyhedral growth of grains separated by sharp grain boundaries. The chemical states of the ions present in the compound were investigated by X-ray photoelectron spectroscopy (XPS) studies, and the electrical pathways were identified. Complex impedance studies were carried out in the experimental frequency and temperature ranges of 40 Hz–4 MHz and 178–408 K, respectively. The equivalent circuit model (RGQG) (RGBQGB) resolves the impedance response into two contributions originating from the intra-grain and inter-granular micro-constituents of the material. The electrical conduction mechanism is based on the Mott variable range hopping model. The complex electric modulus studies demonstrate the short- and long-range mobility of the charge carriers and rule out the presence of electrode effects on the dielectric relaxation mechanism of the material. The decreasing pattern of dielectric permittivity with frequency is explained by the Maxwell–Wagner type of polarization. The frequency dependence of the loss factor exhibits the presence of thermally activated relaxation time distribution in the material.