Gd doping effect on structural, electrical and dielectric properties in HoCrO3 orthochromites for electric applications

Abstract In this work, we investigate the structural, electrical and dielectric properties of HoCrO3, Ho0.9Gd0.1CrO3 and HoCr0.9Gd0.1O3 orthochromites successfully synthesized by the sol-gel process. Our samples were characterized by scanning electron microscopy, energy dispersive and X-ray diffraction (XRD) at room temperature. The XRD analysis shows that the samples crystallize in the orthorhombic system with the Pbnm space group. Depending on frequency in the range [40–107Hz] and temperature in the range [160–440K], the electrical properties were explored by impedance spectroscopy measurements. The obtained results demonstrate that the DC electrical conductivity decreases by doping HoCrO3 with Gd in A-site and increases if Gd occupies the B-site of the perovskite. The parent sample shows a semiconductor behavior until 400K where a transition to a metallic one appears. For doped samples, the transition temperature is estimated at 420K. The AC conductivity measurements can be described by the Jonscher power law and the conduction mechanism can be related to the cationic disorder. Electrical results reveal that the contribution of grains and grain boundaries in the conduction process differs according to the site of the doping by gadolinium. Furthermore, the impedance plots were well described by an adequate equivalent circuit taking into account the contributions of grains and grain boundaries. Colossal dielectric permittivities of the order of 105 F/m are obtained and were attributed to the Maxwell-Wagner interfacial effect. The dielectric losses can be described by Giuntini law and the dielectric relaxation phenomenon is shown to be obscured by the DC-conductivity process. The capacitance values are in the order of 10−2 μF for all studied compounds. These results can conduct the use of our compounds towards the electronic devices industry.