Structural and Electrical Properties of Ca2+ Doped LaFeO3: The Effect of A-site Cation Size Mismatch

Abstract

In this study, nanosized La1-xCaxFeO3 (0.00≤x≤0.40) compounds prepared via sol-gel method followed by heat treatment at 1100oC for 24 hours are studied. Crystal structure, microstructure, surface morphology and temperature-dependent resistivity of the samples are investigated. TEM investigation reveals nanoparticles with an average size of 35nm produced from the sol-gel process. The crystal structure of the compounds belongs to an orthorhombically distorted perovskite structure with Pbnm space group. Lattice distortion and cation size mismatch increase with an increase in Ca and particle and grain growth are suppressed by Ca doping. Electrical conduction is explained via thermally activated hopping of small polarons. Unit cell volume, charge ordering temperature, and activation energy for small polarons decrease linearly with an increase in cation size mismatch. Room temperature resistivity decreases with Ca doping and gets its minimum value for 30% Ca at which the orthorhombic distortion is maximum.

Development of a Graphical User Interface for Reflection Loss Calculation in Perovskite-RGO based Microwave Absorbing Composites

“…However, due to the presence of an additional energy level of RGO, the octahedron perovskite structure shifts from its center of symmetry. The perovskite oxide can show either ferromagnetic or magnetic properties when the electron charge distribution in the B-O-B bond is such that, one of the B cations is empty while the other is half filled following Goodenough-Kamamori's rule on superexchange interactions [14][15], thus increasing the overall magnetic permeability of the compound [23][24].…”

Optimization of a Perovskite-based Multilayer Microwave Absorber using an Equivalent Circuit Model

“…In the B-O-B bond of the perovskite p-orbital of oxygen overlaps with the d-orbital of the B cation on both sides, such that the bond is split to an upper and lower energy orbital. If the charge distribution is such that one of the upper energy levels is half filled for one B-O bond while the other on the opposite side is empty, magnetic dipoles get induced across the perovskite unit cell [11][12][13]. This charge distribution is also affected by the boundary material used in the composite.…”

“…9* . 9*( (11) represents the reflection coefficient of the absorber which depends on the required RL of the absorber as: = : ;< : (12) Solving (12) for the RL range from -20 to -60dB, the constraint equality for function comes out to be: 0.1 < < 0.7…”