MgO Effect on The Dielectric Properties of BaTiO3

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.

Section: Atomic Force Microscopy Analyssmentioning

confidence: 97%

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

Irmak

2020

“…where is the atomic radius of the filler inclusions. In this case it is taken as the pseudo cubic lattice constant of the perovskite structure [25].…”

Section: Theoretical Frameworkmentioning

confidence: 99%

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

Arya

2023

In this paper, a novel method is investigated wherein the theoretical and mathematical analysis of the perovskite-Reduced Graphene Oxide (RGO) based composite microwave absorber is used to form a machine learning model using linear regression to predict the reflection loss and the effective dielectric permittivity of a selected perovskite compound in an RGO-based composite. At first, the theoretical derivation is carried out to find a mathematical relationship between the reflection loss and the dielectric permittivity of the composite and the cationic radii of the perovskite structure, which is then used to form the base for the machine learning model to directly calculate the microwave absorption characteristics from the atomic parameters of the given composite structure. Linear regression is used for the machine learning algorithm which is verified with an R2 of 0.869 with the atomic radii as the input parameters. The model is further used to develop a Graphical User Interface (GUI) to make the prediction more appealing and user-friendly. The current paper provides a new approach to the integration of theoretical knowledge with advanced computing tools to form innovative predictive tools for current microwave-absorbing materials.

“…Permittivity and permeability of a perovskite are affected by different properties of the composite [9]. As shown in Figure 1, the permittivity of perovskites is determined mainly by the nature and amount of polarization occurring across the individual unit cell.…”

Section: Equivalent Circuit Modelmentioning

confidence: 99%

“…where is the angular frequency. With f=2.54×10 9 Hz, the angular frequency is given by ω=2πf=1.59×10 10 /rad/s. Combining ( 1)-( 3), the following equation is obtained:…”

Section: Objective Functionsmentioning

confidence: 99%

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

Arya

2023

In this paper, the optimization of a perovskite-based multi-layer microwave absorber is performed to find an optimized value of the impedance step gradient from the refractive index of the constitutive layers. The optimization presented is unique as it is based on maximizing the dissipation and attenuation ability of the absorber along with a constraint of providing an efficient reflection loss in the absorber. This type of approach ensures the maximum absorption rate of the incident EM waves as the penetrating waves get fully dissipated. Objective and constraint functions are derived from the equivalent circuit model of the multi-layer absorber. The equivalent circuit model is formed using the inductive and capacitive effects across the dielectric and magnetic properties of the constitutive layers. The three layers are composed of perovskite materials with different refractive indexes such that the top layer serves as an impedance-matching layer followed by an alternate dielectric and magnetic layer. It is further shown how the capacitive and inductive losses are dominant over each other in the alternate lossy layers. Empirical relations are used to tabulate the refractive index of a range of perovskite compounds from which suitable combinations can be selected as per the obtained value of the step gradient function. The current work presents a simplistic method to design multi-layer microwave absorbers with different material combinations that are beneficial to the practical applications of microwave absorbers.