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• Dielectric and electrocaloric properties of BCTZ-(Co,Zn)Fe 2 O 4 composite are reported. • ϵ*(102–106 Hz) at different t unfolds domain wall and carrier polarization relaxations. • ∆S dip of the composites increases with x. • 'low tan δ and non-leaky PE loop' is observed in the BCTZ-CZF composite. Dielectric and electrocaloric properties of a multiferroic composite constituted from Ba 0.85 Ca 0.15 Ti 0.9 Zr 0.1 O 3 (BCTZ) and Co 0.4 Zn 0.6 Fe 2 O 4 (CZF), chosen for their closely related transition temperatures, are reported. Dielectric characteristics of the composites in the 1 kHz − 10 MHz angular frequency range are described by two Cole-Cole relaxation models (domain wall and charge carrier) whereas for frequency <1 kHz, it is explained by Maxwell-Wagner type interfacial polarization using Jonscher power law. The effect of CZF phase on the dipolar mechanisms as a function of CZF mole fraction and the temperature are discussed. The electrocaloric property of the composites is estimated indirectly by Maxwell thermodynamic relation. [Display omitted] [ABSTRACT FROM AUTHOR]

The dual role of electric field in the flash sintering process of conducting MnCo 2 O 4 is demonstrated. The flash and conventionally sintered MnCo 2 O 4 samples produced at different temperatures are characterized using energy dispersive X-ray and micro-Raman spectroscopy to elucidate the micro-level spatial distribution of evolved phases. Raman signal mapping over the two ways sintered samples exposes differently grown areas of cobalt oxide based secondary phase. Electrical conductivity of conventionally sintered sample is recorded as a function of temperature and E-field and is utilized to discover the charge carrier activation mechanism during the flash effect. The conductivity before the flash-onset is shown to be comparable to that occurs by Poole-Frenkel effect and Phonon-assisted tunneling i.e. by the mechanism that occurs before the dielectric breakdown of semiconductors and insulators. The observed results, finally, confirm that catalyst like drift action of E-field on cobalt oxide formation is responsible for enhancement in the flash-sintering. [ABSTRACT FROM AUTHOR]

The flash-sintering behavior of manganese cobaltite spinel (MnCo2O4) is analyzed in the present work. It is shown that the MnCo2O4 is flash-sintered at 120–150°C under 15.0–17.5Vcm−1, which is substantially lower than the conventional-sintering temperatures of 1080°C and more. We have also demonstrated that the flash-sintering is a transient phenomenon, where the power dissipation rises quickly at first and then results to Joule heating. The extent of sintering is confirmed through SEM, where a dense and pore-free morphology is observed for the well-sintered samples. The growth of secondary phase as a function of sintering temperature in both conventional and flash processes is monitored by XRD. Consistent changes in I–V curves observed at 200–700°C, suggest that the rapid increase of the conductivity during flash-effect follows the hopping mechanism of usual conductivity phenomenon. On the basis of correlation between the conductivity, phase-stability and microstructure, a mechanism for flash-sintering has been proposed. [ABSTRACT FROM AUTHOR]

Abstract: Nd-doped BiFeO3 thin films were grown by pulsed laser deposition on quartz substrate and their structural, optical and magnetic properties have been studied. X-ray diffraction analysis revealed that Nd addition caused structural distortion even with 5% of Nd concentration, additional secondary phase appeared in all samples but its intensity was greatly reduced with Nd addition. Doping-induced variations in texture and structure modifying both magnetic and optical properties of BiFeO3 thin films. The energy band gap decreases while the refractive index increases with addition of Nd3+ in BiFeO3 for Bi3+. These variations in energy band gap and refractive index have been explained on the basis of density of states and increase in disorders in the system. All the samples were found to exhibit ferromagnetism at room temperature and the saturation magnetization increases with the increase in structural distortion with addition of Nd. Finally, Nd-doping modifies the physical properties of BiFeO3 in comparison to undoped BiFeO3 thin films. [Copyright &y& Elsevier]

Highlights • Performance prediction of SPV modules. • Predictive models include electrical equivalent models and neural networks. • Cascade implementation of 7 parameter and feed forward neural network. • MATLAB GUI developed to predict the SPV module performance. • Five I-V curve parameters determined as a function of temperature and irradiance. • Simultaneous comparison of various predictive models. • Analysis for five SPV module technologies. Abstract Before a photovoltaic (PV) system is installed, a prerequisite modelling and performance analysis are carried out which estimates the performance parameters and reliability in operation of PV system. This paper proposes a neural network approach to performance prediction of PV Modules. Here the feed forward neural networks are used to predict I-V curve parameters as a function on input irradiance and temperature. K Fold cross-validation is used to validate model accuracy for determination of I-V curve parameters for five different technology modules, i.e., CdTe, CIGS, MICROMORPH, MUTICRYSTALLINE, MAXEON. A comparison is also drawn between the neural network predictor and the existing modeling procedures available. Model parameters have been determined following iterative, analytical and regression of known data points for seven and five parameter model of PV Modules. Among the electrical equivalent models, the seven parameter model is the most efficient model for performance prediction however commutation of model parameters in complex and tedious. Neural network model simplifies the computational process at the expense of higher error variance in comparison to electrical equivalent models. Further, a cascade implementation of the above two is designed and tested on Multicrystalline and Maxeon technology modules for higher model accuracy. The results obtained, verify the proposed cascaded model to be the most efficient model in comparison to independent models where mean bias error deviations are less than ±1% and error variance is reduced significantly. Also, a MATLAB based graphical user interface (GUI) is developed that can be used to predict the performance based on the analysis carried out. The proposed model is tested against a set of operating conditions and compared to the actual experimental values obtained using outdoor tests. [ABSTRACT FROM AUTHOR]