Extrinsic Effects on the Impedance Spectra of LaYFe2O6

Abstract

This work represents an effective approach to witness the true impedance profiles of the material. Here, an A-site double perovskite material LaYFe2O6 is prepared by the sol-gel auto combustion method. This material is characterized by the powder X-ray diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), Thermogravimetric Analysis (TGA)-Differential Scanning Calorimetry (DSC), and Electrochemical Impedance Spectroscopy (EIS) technique. The XRD measurement confirms the successful synthesis of the said material with orthorhombic crystal structure having symmetry P21nm (~90%) and a slight contribution from Pbnm phase (~10%). The FESEM image suggests porous nature of the sample having grain size ~150 nm, sintered at 1473 K. TGA with simultaneous DSC measurement shows slight but gradual mass loss (related to the adsorbed gases/vapours) above 400K. The EIS (above-room-temperature region) shows, influence of the adsorbed gases/vapours in the pores of the pellet, on the impedance data. In this context, a homemade open – atmospheric impedance measurement setup (working range up to ~600 K) is developed. The EIS measurement are done for (1) as prepared sample (2) sample preheated to 473 K before performing EIS and (3) sample preheated to 400 K under vacuum. The process giving best result (having minimum effect of the adsorbed gases on the observed impedance spectra) is found by following the method (2); i.e., electroded sample is heated to 473 K in atmospheric conditions and brought back to room temperature to start the measuremen