Department of Physics

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IIT Jodhpur

The samples SrSnO3 (SBS0) and Sr0.98Ba0.02SnO3 (SBS2) were synthesized using sol–gel route, followed by calcination at 1073 K. Rietveld refinement analysis of XRD data shows orthorhombic phase under Pbnm space group. Lattice parameters, volume and density of the doped sample were found to be higher than undoped, due to higher ionic radii of Ba2+. Further, the Raman spectrum of samples was carried out to study the local structure. Optical properties of samples show intense absorption in UV range and transparent in visible to NIR region. The direct bandgap of samples was found to be 3.88 eV and 3.97 eV for SBS0 and SBS2, respectively, reflecting the semiconducting nature of a sample. Dielectric properties of the sample were explained in terms of interfacial and orientational polarization. Temperature-dependent conductivity analysis of the sample reflected an Arrhenius-type charge transport, with two conduction regions in SBS2 and single conduction in SBS0. In the present case, the activation energy value represents a mixed ionic and electronic conductivity of the sample, making it a promising candidate for mixed ionic and electronic conductor device application. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.

World University root node

Journal of Materials Science: Materials in Electronics

Rietveld refinement, optical, dielectric and ac conductivity studies of Ba-doped SrSnO3

Metastable supercooled liquid phase change material (MSLPCM) is prepared by homogeneous mixing of sodium acetate trihydrate (SAT), water and ethylene glycol (EG) in 92:5:3 weight fractions, respectively. A stainless steel (SS-306) triggering disk of size 20 mm (L) × 18 mm (W) × 0.2 mm (T) is fabricated by engraving grooves on SS disk for initiating nucleation in heat pack and release of heat at the time of requirement. The PCM heat pack containing 300 g PCM and a triggering disk is fabricated using high frequency PVC sealing machine. Thermal performance of identical PCM heat pack and water pack (300 g water) is carried out inside temperature history measuring setup at 0 °C ambient temperature. The temperature of PCM heat pack and water heat pack reduces from 70 to 30 °C in 210 and 48 min, respectively at 0 °C ambient temperature. The heating time of PCM heat pack is ~4.4 times more compared to water heat packs. © 2020, Springer Nature Singapore Pte Ltd.

Energy, Environment, and Sustainability

Fabrication and Thermal Performance Evaluation of Metastable Supercooled Liquid PCM Based Heat Pack

Solar selective coatings (SSC) are integral part of the receiver in any concentrated solar thermal system for efficient conversion of incident solar energy into thermal energy. The most common solar thermal systems are based on parabolic trough collectors, which are operating at 350 °C. Thus, the absorber coating should be robust and efficient to operate at such temperatures without any degradation. There are limited such solar selective coatings and very few are commercially available. These are cermet based structure and are stable at high temperature in vacuum. These structures are prone to chemical reaction in open-air condition, which results in degraded optical performance of SSC structures. Thus, there are issues and challenges in SSCs, especially for higher operating temperatures, which is essential to realize the higher efficiency of solar thermal systems. The work is focusing on such constraints towards realizing high temperature solar selective coatings. © 2020, Springer Nature Singapore Pte Ltd.

Smart Innovation, Systems and Technologies

Issue and Challenges with High-Temperature Solar Selective Material for Solar Thermal Application

This paper reports the synthesis of pure and doped lanthanum nickel oxide (LaNiO3) nanoparticles (NPs) using auto-combustion route. Various characterization techniques were employed for the investigation of the effect of transition metal doping on the structural, optical, magnetic and frequency dependent dielectric properties of this system. X-ray diffraction (XRD) results were used to calculate the crystallite size and phase composition of the nanoparticles. The well intense peaks in the XRD pattern confirmed the perfect doping of transition metal ions (Fe, Cr, Co) in the LaNiO3 lattice structure. The scanning electron microscopy (SEM) confirmed the porous surface morphology of the nanoparticles. The presence of various functional groups, stretching and vibrational modes were analyzed by the Fourier Transform Infra-Red (FTIR) technique. The energy band gap (Eg) of the synthesized materials were calculated from the absorbance spectra using Tauc's relation. The band gap was observed to increase with doping indicating blue shift. The frequency dependent dielectric properties were measured at room temperature using LCR meter in the frequency range of 42 Hz to 5 MHz. It was observed that the dielectric constant and dielectric loss decreases with the increase in frequency. This decrease in dielectric constant as well as in dielectric loss with increase in frequency may be attributed to decreased polarization at higher frequency. The dielectric behaviour of LaNiO3 based perovskite oxides is explained on the basis of Koop's theory which is based on Maxwell-Wagner two layer model. Vibrating sample magnetometer (VSM) was used to study the magnetic properties at room temperature and the obtained results confirmed the ferromagnetic nature of all the compositions. © 2019 Elsevier B.V.

Journal of Magnetism and Magnetic Materials

Investigation of structural, optical, dielectric and magnetic properties of LaNiO3 and LaNi1−xMxO3 (M = Fe, Cr &amp; Co; x = 5%) nanoparticles

In this study, an atmospheric pressure dielectric barrier discharge-based argon plasma jet has been modeled using COMSOL Multiphysics, which is based on the finite element method. The fluid dynamics and plasma modules of COMSOL Multiphysics code have been used for the modeling of the plasma jet. The plasma parameters, such as electron density, electron temperature, and electrical potential, have been examined by varying the electrical parameters, that is, supply voltage and supply frequency for both cases of static and with the flow of argon gas. The argon gas flow rate was fixed at 1 l/min. Ring electrode arrangement is subjected to a range of supply frequencies (10-25 kHz) and supply voltages (3.5-6 kV). The experimental results of the ring electrode configuration have been compared with the simulation analysis results. These results help in establishing an optimized operating range of the dielectric barrier discharge-based cold plasma jet in the glow discharge regime without arcing phenomenon. For the applied voltage and supply frequency parameters examined in this work, the discharge was found to be consistently homogeneous and displayed the characteristics of atmospheric pressure glow discharge. Copyright © The Author(s) 2020. Published by Cambridge University Press.

Laser and Particle Beams

Modal analysis of dielectric barrier discharge-based argon cold plasma jet

An electronic counter is an integral component in an analog to digital (A/D) or digital to analog signal conversion circuit. The number of flip-flops (n) in these devices decides the quality of the conversion as the output is proportional to 2n. Since each flip-flop is a combination of transistors, and each transistor occupies some space, there is a limitation in the quality of conversion. The smallest 4-bit asynchronous counter is built by using a self-assembled redox-active organic molecule 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), where each DDQ molecule is acting as an individual flip-flop which is the building block of a counter. These molecules reduce the size of the counter by two orders. The output of the counter is obtained by tracking the translational motion of a group of molecules which are oscillating about the average value concerning the applied bias. Sixteen new spatial locations are obtained corresponding to sixteen distinct analog inputs (bias voltage) to the flip-flops. So, unconventional conversion of an analog signal to ultra-digital (UD) signal is possible by using an n-bit counter consisting of as many numbers of flip-flops and thus can become a system for the conversion of A/UD signal. © 2020 Wiley-VCH GmbH

Department of Metallurgical & Materials Engineering

Advanced Materials Interfaces

Voltage Induced Molecular Motors Constitute the Smallest Self-Assembled Molecular Electronic Counter

Metallo-supramolecular polymers offer ample opportunity to develop new emergent materials with the potential for applications as future memories. In this context, we have synthesized a novel hybrid polymer of our developed Schiff base ligand with Ru(II)-metal ion. The main objective of this study is to understand the effect of changing central metal ion on the ligand field stabilization energy, and the band gap of material as the biting angle of organic moiety changes accordingly with a change in cationic radius of the central metal ion. Furthermore, we have also investigated the application in non-volatile memory devices. Complete characterization of the newly synthesized hybrid polymer has been performed to establish its structure as well as oxidation state of the central metal ion. A comparative study of the present case and the previously reported Fe(II)-polymer provides a clear insight into the effect of incorporating a bigger size metal ion in the polymer chain. Non-volatile memory properties of the polymer have shown a rare behaviour of Negative Differential Resistance (NDR) along with the Low Resistive State (LRS) as its pristine state. Remarkable charge retention and endurance test have also been demonstrated. © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

European Journal of Inorganic Chemistry

Stabilization of Pristine Low Resistive State in a Ruthenium(II)-Polymer of a Hexadentate Schiff Base Ligand: Synthesis, Characterization, and Application as Non-Volatile Memory Device

The sequential, multi-stage crystallization and magnetic hardening behaviour of Fe82B14Si2Nb2, Fe83B13Si2Nb2, Fe83B12Si2Nb2Cu1 and Fe85B13Nb2 melt-spun alloys have been investigated. The microstructure-crystallization-magnetic property relationship was established using X-ray diffractometry (XRD), differential scanning calorimetry (DSC), magnetometry, transmission electron microscopy (TEM) and magneto-optical Kerr effect microscopy (MOKE) techniques. The increase of Fe content (&gt;82 at%) of as-quenched ribbons imparts microstructural heterogeneity across the ribbon cross–section; i.e., textured α-Fe crystals at the free surface to hetero-amorphous microstructure in the bulk matrix. The isochronal annealing of hetero-amorphous alloys depicts simultaneous surface and bulk crystallization process occurring before and after the crystallization onset temperature (Tx1) temperature. The annealing temperature range (Ta &lt; Tx1) coinciding with the paramagnetic region of the thermo-magnetic plot, induces irreversible magnetic hardening due to simultaneous coarsening of pre-existing crystal nuclei and exchange de-coupling between nanocrystal and intergranular matrix. The onset of primary crystallization in the pre-crystallized ribbons results in bimodal nanocrystallite distribution having an average crystallite size exceeding the ferromagnetic exchange length of Fe-based alloys. The minor Cu addition alters the growth morphology of pre-existing nuclei from dendrite-like to equiaxed, assisting heterogeneous nucleation and improving intergranular amorphous stability by delaying boride precipitation. The soft-magnetic property deterioration of partially crystallized ribbons is discussed within the framework of Extended-Random Anisotropy models. © 2020 Elsevier B.V.

Crystallization and magnetic hardening behaviour of Fe-rich FeSiBNb(Cu) melt-spun alloys

We study the topological properties of multiple optical bound states in the continuum using continuous parameter tuning. We utilize the formation of ultra-high- Q resonances to investigate the potential of quality-sensing in a speciality optical microcavity. © 2020 IEEE.

2020 Conference on Lasers and Electro-Optics Pacific Rim, CLEO-PR 2020 - Proceedings

Ultra-high sensitivity near multiple bound states in the continuum in microcavity resonators

The dynamical encirclement around a second-order exceptional point (EP) and corresponding chirality driven nonadiabatic modal dynamics have attracted enormous attention in the topological study of various non-Hermitian systems. However, dynamical encirclement around multiple second-order EPs in a multistate system is yet to be explored. Here, exploiting an exclusive design of a planar gain-loss assisted three-mode supported optical waveguide with local Kerr nonlinearity, we encounter multiple second-order EPs. Judiciously, choosing a specific parameter space by varying the unbalanced gain-loss profile, we encircle multiple EPs simultaneously, and explore the beam dynamics toward corresponding chiral or nonchiral aspects of the device. While propagating through the designed waveguide, three coupled modes are collapsed into a specific dominating mode, owing to corresponding nonadiabatic corrections around multiple EPs. We reveal that in the absence of chirality the same amount of focusing-and defocusing-Type nonlinearity gives different dominating output, irrespective of the choice of inputs, for the same topological structure of the waveguide. An analytical model to describe this anomalous mode collapsing phenomenon due to interplay between nonlinearity and the EP has been developed. Our findings should provide a promising opportunity to switch or retrieve a selective mode from a multimode signal in integrated devices. © 2020 American Physical Society.