Gaurav Vats

Piezoelectric material selection for transducers under fuzzy environment

Piezoelectric ceramics are extensively investigated materials for transducer application. The selection of optimal piezoelectric material for this particular application is a tedious task. It depends upon various physical properties, including piezoelectric charge coefficient (d33), electromechanical coupling factor (Kp), dielectric constant (ɛr), and dielectric loss (tanδ). The classical multiple attribute decision making (MADM) can be used for decision making if these properties are known precisely. However, these properties cannot be expressed by exact numerical values, since they are dependent upon the microstructure and fabrication process. Fuzzy-based MADM approaches can be helpful in such cases. In this paper, we have determined the ranks and rank indices (for degree of closeness) of important piezoelectric materials using fuzzy VlseKriterijumska Optimisacija I Kompromisno Resenje (VIKOR) technique. PLZT(8/65/35) ((Pb1−xLax)(ZryTi1−y)O3) and KNN-LT-LS ((K0.44Na0.52Li0.04)-(Nb0.84Ta0.10Sb0.06)O3) consecutively are found to be the top-rank piezoelectric ceramics. This indicates that KNN-LT-LS can be used on behalf of lead-based piezo-ceramics.

Giant pyroelectric energy harvesting and a negative electrocaloric effect in multilayered nanostructures

This work examines the potential of PbZr0.53Ti0.47O3/CoFe2O4 (PZT/CFO) multi-layered nanostructures (MLNs) to achieve a giant electrocaloric effect (ECE) and enhanced pyroelectric energy harvesting. Unlike the conventional ECE, the effect of PZT/CFO MLNs is governed by dynamic magneto-electric coupling (MEC) and can be tuned by the arrangement of various ferroic layers. The ECE is investigated in the stacks of three (L3), five (L5) and nine (L9) alternating PZT and CFO layers. Intriguingly, all configurations exhibit a negative ECE, calculated using Maxwell relations, which has a high magnitude in comparison with the previously reported giant negative ECE (|ΔT| = 6.2 K). The maximum ECE temperature change calculated in three (L3), five (L5) and nine (L9) layers is 52.3 K, 32.4 K and 25.0 K respectively. In addition, the maximum pyroelectric energy harvesting calculated for these layers using a modified Olsen cycle is nearly four times higher than the highest reported pyroelectric energy density of 11 549 kJ m−3 cycle−1. This increase is attributed to the cumulative effect of multiple layers that induce an enhancement in the overall polarization, 1.5 times of lead zirconate titanate, and leads to abrupt polarization changes with temperature fluctuations. The present study also sheds light on material selection and the thermodynamic processes involved in the ECE and it is concluded that the refrigeration obtained from the reversed Olsen cycle is a combined effect of an isothermal entropy as well as the adiabatic temperature change.

Selection of optimal electronic toll collection system for India: A subjective-fuzzy decision making approach

Present study deals with the adoption of newer technologies for developing nations. Most of the developing countries due to lack of resources perform techno-socio-economic analyses on the already existing models of the developed ones. Such adopted technologies may not perform effectively because of unlike socio-economic factors. Hence, it becomes important to select new technologies based on appropriate and suitable criteria with respect to a particular country. In this paper, we have demonstrated selection of optimal electronic toll collection (ETC) system for India. In this context, we have considered thirteen crucial parameters for selection of appropriate ETC system. Cost is found to be the pivotal selection criterion in India. Further, fuzzy logic based MADM (multiple attribute decision making) approach is employed for selection of optimal ETC system for India. RFID-based (radio frequency identification) ETC is found to be the most suitable alternative among all considered ETC technologies. Our results are in strong agreement with the report of apex committee, appointed by “Government of India (Ministry of Road Transport & Highways)” for implementation of ETC in India.

A Prime Lead-Free Ferroelectric Ceramic for Thermal Energy Harvesting: 0.88Bi0.5Na0.5TiO3-.02SrTiO3-0.1Bi0.5Li0.5TiO3

Present study unfurls the colossal energy harvesting potential of lead-free 0.88Bi0.5Na0.5TiO3-.02SrTiO3-0.1Bi0.5Li0.5TiO3 (BNT-ST-BLT) bulk ceramic using Olsen cycle. This material has been reported for its excellent ferroelectric properties in various aspects. The maximum harness-able energy density for this composition is found to be 2130 J/L in the temperature spectrum of 20–140°C and applied electric field of 0.1-6.0 MV/m. We found that the energy density of this material is 2.6 times higher than the maximum energy density documented for any lead-based ferroelectric ceramics reported to date. Prior to the present study, 8/65/35 PLZT (thick films) was reported for the highest energy density of 888 J/L (temperature range: 25–160°C; applied electric field: 0.2-7.5 MV/m).

Enormous energy harvesting and storage potential in multiferroic epitaxial thin film hetrostructures: an unforeseen era

This work propounds the competence of epitaxial multiferroic thin-film heterostructures for low-grade thermal energy harvesting using Olsen cycle and ultra-high density capacitor applications. Our investigation (based on well-reported experiments in the literature) reveals that this class of materials shows a giant energy storage density as well as colossal energy harnessing possibilities. Indeed, the energy storage capability of these films is found to be 1.6 times the already existing giant value (alkali free glasses: 35 MJ m−3). On the other hand, the energy harnessing plausibility is found to be four orders of magnitude higher than the reported values to date.

Pyroelectric control of magnetization for tuning thermomagnetic energy conversion and magnetocaloric effect

Tri-layered PbZr0.53Ti0.47O3/CoFe2O4/PbZr0.53Ti0.47O3 (PZT/CFO/PZT) nanostructures have been reported to have the highest pyroelectric energy harvesting and electrocaloric effect. These nanostructures are magnetically active and the resultant ‘giant’ effects are considered to be governed by dynamic magneto-electric coupling. Therefore, it is of interest to investigate such nanostructures for thermomagnetic energy conversion and its corresponding magnetocaloric effect (MCE). In this context, the present study reveals that ferroelectric/magnetic/ferroelectric multilayered nanostructures of PZT/CFO/PZT can be used to achieve pyroelectric control over magnetization even in the absence of an applied electric field. Using the same phenomena, the coexistence of a ‘giant’ positive and a negative MCE is attained in the tri-layered PZT/CFO/PZT nanostructures for identical temperature ranges, but with different levels of applied magnetic field. Unlike conventional structural phase transitions based MCE effects, the present study demonstrates the possibility of obtaining a giant MCE simply by pyroelectric control of magnetism. The MCE entropy changes (ΔS(H)max = 1.5 J kg−1 K−1 for inverse MCE and 18.15 J kg−1 K−1 for positive MCE at 245 K) calculated using Maxwell equations are found to be as large as those reported for existing giant MCE systems. Moreover, our investigation of the thermomagnetic energy conversion in these nanostructures indicate that the tri-layer configuration also has a giant thermomagnetic energy conversion efficiency of 41% relative to that obtained using the Carnot cycle.

Giant energy harvesting potential in (100)-oriented 0.68PbMg1/3Nb2/3O3–0.32PbTiO3 with Pb(Zr0.3Ti0.7)O3/PbOx buffer layer and (001)-oriented 0.67PbMg1/3Nb2/3O3–0.33PbTiO3 thin films

This work emphasis on the competence of (100)-oriented PMN–PT buffer layered (0.68PbMg1/3Nb2/3O3–0.32PbTiO3 with Pb(Zr0.3Ti0.7)O3/PbOx buffer layer) and (001)-oriented PMN–PT (0.67PbMg1/3Nb2/3O3–0.33PbTiO3) for low grade thermal energy harvesting using Olsen cycle. Our analysis (based on well-reported experiments in literature) reveals that these films show colossal energy harnessing possibility. Both the films are found to have maximum harnessable energy densities (PMN–PT buffer layered: 8 MJ/m3; PMN–PT: 6.5 MJ/m3) in identical ambient conditions of 30–150°C and 0–600 kV/cm. This energy harnessing plausibility is found to be nearly five times higher than the previously reported values to date.

Application Oriented Selection of Optimal Sintering Temperature from User Perspective: A Study on K0.5Na0.5NbO3 Ceramics

This work presents a novel user oriented approach that can relate materials science with technological applications in a more transparent, systematic and efficient manner. We have made an attempt to figure out the optimal (corresponding to best combination of material properties) sintering temperature of K0.5Na0.5NbO3 (KNN) for transducer and electrical energy storage applications. The weights and priority of vital physical properties for applications understudy are calculated using the quality function deployment (QFD) method. Losses (tanδ), charge storage properties (ϵr, Pr and EC) and elastic compliance (sE12 and sE11) are found to have negative priority for transducer application while in the other case d31, tanδ, sE12 and sE11 are spotted to have negative priority. Priority order for transducer and energy storage application is d31>kp>QM>Tc>tanδ>ϵr>Pr=EC=sE12=sE11>ρ and ϵr>d31=tanδ>sE12=sE11>Tc>Pr>EC>kp>ρ>QM, respectively. Finally, 1080°C (transducer) and 1120°C (capacitor) are the found to be the most appropriate solutions among the alternatives under using modified analytic hierarchy process (AHP).

Effects of morphotropic phase boundary transitions and structural transformations on Olsen cycle assisted thermo-electrical energy conversion: A case study on Bi0.5Na0.5TiO3-xBaTiO3 system

Abstract This article reports the peculiarity in the thermo-electrical energy conversion (by Olsen cycle) capability of Bi0.5Na0.5TiO3-xBaTiO3 (BNT-BT) system caused by the coupled effect of structural transformations and phase transitions in vicinity of the morphotropic phase boundary (MPB). The calculated maximum energy density estimated for nearly identical ambient conditions for MPB (x = 0.06) lies in the range of 40–110 J/L (40–110 kJ/m3) while moving away from the MPB the same elevates dramatically on both the ends. The utmost energy density found in system is 1000 J/L (1000 kJ/m3) for BNT-0.3BT (temperature range: 42.6–108.7°C; applied electric field: 0–6.5 MV/m). This energy density is significantly higher than the reported thermo-electrical energy generation (680 kJ/m3) using negative electrocaloric effect in BNT-xBT systems. It is found that ferroelectric to antiferroelectric transition as well as transformation suppresses harvested energy density at MPB. Contemporary, rhombohedral to tetrahedral transitions contributes towards enhancement in the energy harnessing capability of the system. Consequently, it is revealed that in contrast to the rombohedral phase (a = b = c) the non-centro symmetric disturbances caused by thermal fluctuations in tetrahedral phase (a≠c) are higher and facilitate the domain wall switching leading to magnification of energy density.

An insight into thermal and vibration cyclic energy harvesting using ferroelectric ceramics

This article reviews the basics of ferroelectric energy harvesting cycles based on thermal fluctuation and mechanical confinement. In this context, five cycles (Olsen cycle, Clamped Olsen cycle, Electro-Mechanical cycle, Thermally Biased Electro-Mechanical cycle and New Power cycle) are studied for two different compositions (0.94Bi1/2Na1/2TiO3–0.06BaTiO3: BNT–6BT; 0.91(Bi1/2Na1/2)TiO3–0.07BaTiO3–0.02K0.5Na0.5NbO3: BNT-BT-KNN;) which represents two distinct classes (based on domain wall rotation/motion) of ferroelectric materials. These can be classified as the composition with dominating impact of mechanical forces while the other is with ascendant thermal effects over the domain wall behavior.