Raman, dielectric and variable range hopping nature of Gd2O3-doped K0.5N0.5NbO3 piezoelectric ceramics

(K0.5Na0.5)NbO3 (KNN) + x wt% Gd2O3 (x = 0 -1.5) ceramics have been prepared by conventional solid state reaction method. The effect of Gd2O3 on the structural, microstructural and dielectric properties of KNN ceramics were studied systematically. The effect of Gd2O3 on phase transformation from orthorhombic to psuedocubic structure is explained interms of changes in the internal vibration modes of NbO6 octahedra. The Raman intensity of the stretching mode v1 enhanced and shifted toward higher wavenumber with Gd2O3 concentration, which is attributed to the increase in polarizability and change in the O-Nb-O bond angles. Microstructural analysis revealed that the grain size of the KNN ceramics decreases from 2.26 ± 1.07 μm to 0.35 ± 0.13 μm and becomes homogenous with an increase in Gd2O3 concentration. The frequency dependent dielectric spectra are analyzed by using Havriliak-Negami function. The fitted symmetry parameter and relaxation time (τ) are found to be 0.914 and 8.78 × 10−10 ± 5.5 × 10−11 s, respectively for the sample doped with x = 1.0. The addition of Gd2O3 to the KNN shifted the polymorphic phase transition orthorhombic to tetragonal transition temperature (TO-T) from 199oC to 85oC with enhanced dielectric permittivity (ε′ = 1139 at 1 MHz). The sample with x = 1.0, shown a high dielectric permittivity (ε′ = 879) and low dielectric loss (<5%) in the broad temperature range (-140oC – 150oC) with the Curie temperature 307 oC can have the potential for high temperature piezoelectric and tunable RF circuit applications. The temperature dependent AC-conductivity follows the variable range hopping conduction mechanism by obtaining the slope -0.25 from the ln[ln(ρac)] versus ln(T) graph in the temperature range of 133 K-308 K. The effect of Gd2O3 on the Mott’s parameters such as density of states (N(EF)), hopping length (RH), and hopping energy (WH) have been discussed

Boosting the lifespan of magneto-mechano-electric generator via vertical installation for sustainable powering of Internet of Things sensor

Sustainability is essential for magneto-mechano-electric (MME) energy harvesters that convert low-frequency magnetic noise into useful electrical energy to be considered a practical power source for implementing real-life Internet of Things (IoT) sensor networks. In this study, we propose a vertically installed MME energy harvester based on a piezoelectric lead magnesium niobate-lead zirconate titanate (Pb(Mn1/3Nb2/3)O3-Pb(Zr,Ti)O3, PMN-PZT) single-crystal macro fiber composite cantilever. The MME harvester generates 12.2 mW output power from a low-amplitude stray magnetic field of 2.5 Oe and exhibits a long-term usable lifetime of 2.5 × 109 cycles while maintaining over 90 % of its output. An accelerated life test method is employed to predict the usable lifetime of the MME harvester using an inverse power law-Weibull model with accelerating stress of magneto-mechanical vibration-induced strain. In addition, a standalone wireless environmental monitoring system is demonstrated to operate for 10 weeks by exploiting the harvested power from stray magnetic fields (~2.2 Oe) near the power cables of home appliances. This study paves the way for lifetime assessment and prediction of sustainable MME harvesters to increase the practicability of self-powered IoT devices in smart infrastructures. © 2022 The Author

Ceramic-Based Dielectric Materials for Energy Storage Capacitor Applications

Materials offering high energy density are currently desired to meet the increasing demand for energy storage applications, such as pulsed power devices, electric vehicles, high-frequency inverters, and so on. Particularly, ceramic-based dielectric materials have received significant attention for energy storage capacitor applications due to their outstanding properties of high power density, fast charge–discharge capabilities, and excellent temperature stability relative to batteries, electrochemical capacitors, and dielectric polymers. In this paper, we present fundamental concepts for energy storage in dielectrics, key parameters, and influence factors to enhance the energy storage performance, and we also summarize the recent progress of dielectrics, such as bulk ceramics (linear dielectrics, ferroelectrics, relaxor ferroelectrics, and anti-ferroelectrics), ceramic films, and multilayer ceramic capacitors. In addition, various strategies, such as chemical modification, grain refinement/microstructure, defect engineering, phase, local structure, domain evolution, layer thickness, stability, and electrical homogeneity, are focused on the structure–property relationship on the multiscale, which has been thoroughly addressed. Moreover, this review addresses the challenges and opportunities for future dielectric materials in energy storage capacitor applications. Overall, this review provides readers with a deeper understanding of the chemical composition, physical properties, and energy storage performance in this field of energy storage ceramic materials

Effect of elastic modulus of cantilever beam on the performance of unimorph type piezoelectric energy harvester

Piezoelectric energy harvesting is a technique that can utilize ambient vibration energy to generate useful electrical energy, which is promising for powering small-scale autonomous devices such as sensors for wearable, biomedical, and industrial applications. Typically, cantilever-type piezoelectric energy harvesters (PEHs) are operated under resonance condition to achieve the maximum output power at low frequency stimuli. Along with resonance matching, it is also necessary to optimize the PEH configuration with high electromechanical properties for the efficient energy conversion. The purpose of this study is to investigate the effect of the elastic modulus of the passive layer in the cantilever structured PEH on the electromechanical properties and thus harvesting performance. In this regard, two unimorph type PEHs having the identical geometry, piezoelectric properties, and proof mass but with different elastic modulus (55 GPa and 97 GPa) of Ti alloy-based passive layers were fabricated and their output performance was compared under the same acceleration amplitude excitation stimuli. The PEH with the smaller elastic modulus passive layer exhibited almost 53% improvement in the maximum power than that with the higher elastic modulus passive layer, which is attributed to a smaller mechanical damping ratio, higher quality factor, and larger vibration amplitude

Effect of Thickness Ratio in Piezoelectric/Elastic Cantilever Structure on the Piezoelectric Energy Harvesting Performance

The energy harvesting by utilizing the piezoelectric effect for the conversion of oscillatory mechanical energy to useful electrical energy has been promising for self-powered devices. The output power can be controlled by designing the size and shape of the constituents of the harvester. This study demonstrates the effect of Ti plate (elastic layer) thickness on the resonant frequency, neutral axis position, vibration amplitude and energy harvesting performance of the cantilever structured piezoelectric energy harvester (PEH). Here, the each harvester had the same dimensions of piezoelectric layer and the same proof mass position at the end of the cantilever while it had the different elastic layer thicknesses (70-300m). The analysis revealed that the output power showed the opposite trend in vibration amplitude with varying the elastic layer thickness. Among all of the PEHs, the configuration with the largest elastic layer thickness (300m) exhibited a maximum output power of 48W at 76Hz under 0.2g acceleration, despite of the smallest vibration amplitude and the highest resonant frequency. The outcomes suggest that the thickness ratio of the piezoelectric and elastic layers should be optimized to realize the best harvesting performance. [GRAPHICS] .1