Invited Speakers

Invited Speakers

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PROF. A K NIGAM

TIFR, Mumbai
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    During the past few decades, a great deal of interest was generated in the study of perovskite oxides, particularly after the discovery of high-Tc superconductivity, colossal magnetoresistance (CMR), etc. Many of these oxides have also been reported to exhibit multifunctional properties. In recent years, isostructural compounds called antiperovskites have also attracted attention, after the observation of superconductivity in MgCNi3, and also due to observation of giant magnetoresistance (GMR), negative or zero thermal expansion (NTE/ZTE), etc. in other similar compounds. Mn-based antiperovskite compounds have attracted considerable interest as a candidate for ferroic cooling applications. Amongst these Mn3GaC undergoes a volume discontinuous first order transition from ferromagnetic to antiferromagnetic ground state around 160 K, accompanied by a large magnetocaloric effect (MCE). A systematic study on effect of Sn substitution on Mn3GaC compound reveals that the nature of the MCE has a strong dependence on the type of magnetic ordering. The results of this study would be presented and discussed in this talk.

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PROF. ARGHYA TARAPHDER

Department of Physics,
IIT Kharagpur
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Topic of Talk : Emergent metallic layer, superconductivity, magnetism, defects and Lifshitz transition in the oxide hetero-interface
    The emergent two-dimensional electron liquid (2DEL) at the hetero-interface between two oxide insulators show further emergent phenomena like finite-momentum superconductivity coexisting with inhomogeneous ferromagnetism, superconductor (or metal) to insulator transition, as well as very complex excitations. The role of disorder on superconductivity and ferromagnetism at the interface is crucial: phase segregated regions of superconductivity and ferromagnetism coexist ruling out the FFLO mechanism [1]. The O-defects at the interface affect anti-site order [2] and carrier concentration. These are investigated using Monte Carlo and first-principles techniques. The O-vacancy can bring about metallic behaviour in the otherwise insulating heterostructures [2]. The oxygen vacancy-clustering sheds light on phenomena like carrier freeze-out at low temperature and pseudo-gap in the superconducting state. A perpendicular magnetic field can give rise to a zero-bias anomaly in tunnelling spectrum [3] and topological superconductivity at the core of a vortex. Discovered by Kumar, et al. [4], a transient superconducting state above the nominal Tc implies a 'hidden' superconducting order [5]. Our DMFT calculations [6] predict that the Lifshitz transition (LT) appears to be more prominent in the Seebeck effect rather than in Hall number. The recent observations on the change of sign of magnetoresistance are discussed.

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Prof. A. S. Patra

Professor & H.O.D. Department of Physics, Sidho-Kanho-Birsha University, Purulia, West Bengal
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Topic of Talk : Integration of FTTH and Ethernet Transmission in a WDMPON using Reflective Semiconductor Amplifier and Polarization Multiplexing Technique
    In this paper, a bidirectional WDM-PON architecture has been investigated and demonstrated to transmit 2.5 Gbps and 10 Gbps single over 50 km single mode fiber (SMF) employing polarization multiplexing (POLMUX) technique at OLT and ONU. The polarization multiplexing technique is exercised by polarization beam splitters (PBSs) and polarization beam combiners (PBCs) in our system. Mach-zehnder modulator (MZM) and reflective semiconductor optical amplifier (RSOA) have been used for modulation at optical line terminal (OLT) and optical network unit (ONU) respectively. The downlink and uplink transmission performances are observed by eye diagrams and bit error rate (BER) values, obtained in BER analyzer. Our architecture is efficient to provide various types of convenient services like HDTV and FTTX etc, over long haul fiber link simultaneously and bidirectionally.

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PROF. ANANTHAKRISHNAN SRINIVASAN

Deptt. of Physics, IIT Guwahati, Guwahati
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    Though Ni2MnZ (where Z = Ga, In, Sn, ...) based alloys have been identified as magnetic actuator and environment friendly magnetic refrigerant materials, most of efforts have focused on the bulk alloys. Recently, there has been a keen interest to develop Ni2MnZ magnetic thin films for use in high frequency devices like high-density magnetic recording, magnetic switching, micro inductors, micro transformers, etc. In general, these thin films exhibit properties which are quite different from those of their bulk counterparts due to geometrical, microstructural, and substrate related constraints. Moreover, magnetic properties of these films are strongly dependent on the crystal structure, composition, and sample preparation and processing conditions. Hence, a careful investigation of the structure, magneto-static and magneto-dynamic properties of these films is required to find a material best suited for the above applications. Microwave absorption is a simple but powerful technique which can provide us information on the all the above aspects of the thin films. An electron spin resonance spectrometer operating with a cavity tuned to ~9 GHz with frequency modulation of 100 kHz is a sensitive tool for recording microwave absorption spectra as a function of film orientation with respect to the applied field. In this talk, recent results obtained on microwave absorption in off-stoichiometric Ni2MnZ (Z = Sn, In) based thin films will be presented. Data obtained from structural, morphological, and magnetometry studies on these samples will also be used in the discussions on the analysis of the non-resonant and resonant microwave absorption signals obtained in these studies. Apart from new the physics and material characteristic unraveled by these investigations, possible new applications expected for these films will also be mentioned in the talk.

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PROF. Atiar Rahaman Molla

Senior Scientist
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    In recent times bismuth based layered structured perovskite ferroelectric materials have attracted much attention because of their low leakage current, low operating voltage, fast switching speed, high fatigue endurance and low leakage current density for integrated device applications in non-volatile ferroelectric random access memories (RAM). Ferroelectric materials also possess spontaneous polarization (Ps) resulting from built-in electrical dipoles in their crystal structure. The resulting structural anisotropy gives rise to a host of nonlinear optical properties such as the electro-optic effect, harmonic generation, and photo refraction etc. These properties are useful for optical amplification, switching, sensors, transducers, actuators, etc. In general, glass ceramic dielectrics exhibit high dielectric constant and high breakdown strength simultaneously, with low dielectric loss of ferroelectric glass-ceramics open up enormous possibility for high energy storage applications which can effectively address global air pollution, energy deficiency, climate change and global warming issues by storing and supplying the electricity generated through alternative renewable sources. The advantages of glasses containing ferroelectric crystals as compared to crystals prepared by traditional methods (e.g., the Czochralski technique or sintering) stems from the simplicity of preparation and the possibility of modifying the properties of these glasses by changing the morphology of the precipitated crystals, namely their size, shape, and volume fraction and transparent characteristics of glass can be retained. In order to maintain optical transparency, the process of nucleation and crystal growth requires great control when the size of crystals dispersed in the glass matrix are not large enough to cause light scattering. For the most electrical applications, it is necessary that the crystals have a size sufficient to present, a ferroelectric response and these two attributes represent a difficult tradeoff. In this paper it will be presented how we can utilize crystallization kinetics studies for controlling crystallization of glasses in order to tailor properties and size of the crystallites for achieving sufficient transparency. For example, the crystallization kinetics of Eu3+ doped K2O-SiO2-BaO-Bi2O3-Ta2O5 (BBTE) glass system was studied using various reaction models like Kissinger, Augis-Bennett, Ozawa, Matusita, Avrami-Erofeev and model free analysis with Friedman method. The activation energies (Ea) for the first crystallization peak (Tp1) are calculated from the reaction models. Homogenous nucleation with an interface controlled crystal growth between two and three dimensions is predicted from the Avrami indices (n) obtained using Matusita (n = 3.5) and Avrami-Erofeev (n = 2.6) reaction models. Prediction of optimum ceramization schedule (i.e. heat-treatment temperature and time) has been possible using the Avrami-Erofeev model and transparent glass-ceramics containing ferroelectric, nanocrystalline BaBi2Ta2O9 crystal phase could be produced. Other than BBTE, in this paper synthesis of few novel, transparent ferroelectric glass-ceramics (TFGC), such as Bi4Ti3O12, BaBi4Ti4O15 etc. their properties and applications will be presented.

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PROF. C S SUNANDANA

School of Physics, University of Hyderabad, Hyderabad
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    Graphene production is the holy grail of current R& D effort. Laboratory-based 'protected environment' routes are many.including rapid thermal annealing[1]. Very significantly, recent synthesis efforts focus on 'rough and ready' kitchen recipes using bio products such as vegetable oils as precursors. This presentation is a brief overview of 'expeditions along the graphite-graphene highway'.It is necessary to emphasize that whatever one does the final product is visualized as a very thin (submicron thick) crystalline film of few-layer carbon. In the latter strong intralayer covalent forces remain exclusively while the weak van der Waals dispersion forces have been almost excluded. The use of a vegetable oil - soybean oil, 'cooked' under ambient atmospheric conditions is an interesting recent approach to graphene synthesis. After a brief mention of the synthesis steps, we consider a mechanism of formation that could be common to all such oil-based precursors. Finally the emerging area of vegetable oil-based polymer production[2] with important implications to environmental issues such as bio degradablilty is briefly discussed . [1] J. R. Prekodravac et al, Mat. Res. Bull. 68(2017)114 [2] Y Zhou et al., Nature 540(2016)354.

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PROF. CHINTAMANI DAS

Programme Officer (BSC), BARC, Mumbai
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    Corrosion is the loss of useful properties of a material due to its interaction with the environment. Mitigation of corrosion can be achieved by reducing the corrosive effect of the environment by forming in-situ surface film on the substrate through addition of inhibitor or a gas. Liquid lead bismuth eutectic (LBE) has been proposed to be used as spallation target and coolant in Accelerator Driven Systems (ADS) in India's nuclear program. Steels undergo corrosion in LBE depending on alloy composition, operating temperature, flow velocity and temperature gradient. Non-isothermal LBE loop may experience preferential dissolution in the hotter and precipitation in colder temperature regions. Zirconium (Zr) and Titanum (Ti) function as inhibitors in LBE by forming in-situ surface film of ZrN, TiN or ZrC, TiC on steel surface and require adequate supply of C and N from the steel and therefore have limited success. Most effective method for reducing corrosion of steel in LBE is by maintaining oxygen concentration in the eutectic to form and maintain in-situ formed protective oxide film on the steel surface while preventing precipitation of lead oxide. In aqueous solutions, on the contrary, organic inhibitors are added to form adsorbed surface film at the metal/solution interface. This chemisorbed or physically adsorbed layer protects the metal from corrosion. Results from exposure of SS316L and 9Cr-1Mo steel in non-isothermal flowing LBE at temperatures of 350 and 450 C for 4000 h with the injection of oxygen of 4 x 10-7 wt % into LBE are presented. Mitigation of corrosion of carbon steel in a typical organic acid mixture using inhibitor is also discussed.

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PROF. GOVIND PRASAD KOTHIYAL

Chairman, MRSI Mumbai Chapter
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    Silico-phosphate glass/glass-ceramics form a biologically active bone materials (hydroxyapatite) layer on the surface that permits bonding with bone and soft tissues. Formation of bone material such as hydroxyapatite is influenced by the addition of different additives and the process conditions followed for base glass/glass-ceramics. In this talk we shall discuss some silico-phosphates prepared by melt quenching and sol-gel processes and investigate their structural and magnetic properties along with bioactivity. We have studied the effect of addition of Fe2O3, ZnO, Ag, and polymer in different silico-phosphate glass systems. We shall report some recent results based on X-ray diffraction, thermal analysis, electron microscopic, and magnetic measurements on both melt and sol-gel derived nano-crystalline silico-phosphate glass/glass-ceramics and nano-composites. Role of additives on particle size, morphology, bioactivity, magnetisation etc will be brought out. Influence of phosphate precursors such as P2O5 or H3PO4 or ((NH4)2HPO4) on the structure, crystallization behaviour and bioactivity of sol-gel derived 45S5 bioglass will be brought out. It was inferred that with (NH4)2HPO4 as the phosphate precursor, it is possible to obtain fully amorphous material with a composition close to bioglass 45S5. Growth of HA on the surface of glass and glass-ceramic pellets with immersion time has been studied and figure shows the growth of HA and particle size on sol-gel derived bioglass material. Glass-ceramic surface helps in the growth of larger HA crystallites. Further Sol-gel derived samples have been found to exhibit superior bioactivity as compared to the bulk melt derived counterparts.

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PROF. P. N. GAJJAR

Department of Physics, Gujarat University, AHMEDABAD
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Topic of Talk : State of Art Model of Thermal Diode and Thermal Transistor - Basic Building Blocks for Controlling Flow of Phonons at Low Dimension
    When we use any mechanical, electrical or electronic equipment/device, it generates redundant heat. Our attempts are always to reduce/pump-out that heat from the equipment/device. To minimize such heat effects, lubricants / coolants / heat exchangers / heat sinks / reflecting thin films / etc... are developed. We have never thought neither made any rigorous efforts to use this heat or store this heat for its fruitful use at later stage. Scientists have made sufficient progress in developing devices based electronics, spintronics, and photonics. But the progresses to design and develop the devices that can utilize the flow of phonons are still very rare. The most important requirement to utilize the heat is to have a material which allows us to control the flow of heat in desire direction and/or stores the heat for longer time. In the present talk, the model of thermal diode will be presented. Thermal diode - a two-terminals thermal device that can be used as a thermal switch and a thermal rectifier. Thermal characteristics of such a thermal diode will also be presented in forward and reverse thermal biased conditions. Very recently, we proposed first ever thermal transistor characteristics. Concept of thermal fourier region, thermal knee point, thermal pinch-off temperature, thermal saturation region/thermal pinch-off region/thermal amplification region be presented in the talk for the model of thermal transistor. The constructed equations for different thermal quantities like source thermal resistance (RT)S, drain thermal resistance (RT)D, thermal transconductance (gm) and thermal amplification factor (a), thermal saturation current will also be presented. Talk will also discuss the challenges ahead in manipulating phononic flow. Few futuristic applications and possibilities of thermal circuitries will remain the part of the talk.

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PROF. MICHAL PIASECKI

Jan Dlugosz University, Poland
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    The crystal structure of the chalcogenide compounds offers a possibility for partial or complete substitution of cation or anion groups, i.e. formation of solid solutions, whose properties can be significantly different from those of pure compounds. The crystal structure of chalcogenides depends on their composition and they are widely used for solar cell, radiation detectos and thermoelectric applications, since they can be grown in the form of thin films. The band structure parameters of these materials are influenced by intrinsic defects forming the additional trapping levels within the host`s band gap. Such defects can significantly change the optical properties of a material, considerably enhance its optical absorption and, therefore, they play a principal role for the optoelectronic and photovoltaic applications. Recently, the new promising direction of investigation was initiated: the growth distorted nano size objects (ultra-thin films ), which possess crystal structure at the edge corner between all the known chalcogenide phases. As results, in the new structures were observed not only amelioration the useful parameters but also was seen new, unexpected properties, which do not have their bulk precursors. The complex approach, which includes theoretical analysis based on the DFT methods supported by the experimental studies by XPS is a very powerful tool for predicting the optoelectronic features of the materials used for the thermoelectricity and solar panels. It also allows for modelling the defects properties and their influence on the host`s properties . Nowadays considerable progress has been achieved in the development of experimental methods of the CGC production. At the same time, very rapid advances in reliable computational DFT-based methods have paved a broad way towards increasing importance of so-called ``theoretical experiments``, when thoroughly performed calculations replace or forego experiments and even predict unknown materials and their properties. Such ``theoretical experiments`` are relatively cost less, if compared to the real laboratory activities; however, the results of such calculations serve as extremely useful guides for setting up a proper direction in search for new efficient materials.

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PROF. MAHESH KUMAR

IIT Jodhpur
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    Continued growth of industrialization has led to the emission of various toxic and combustible gases. Among them, NO2 is one of the most poisonous gases which are mainly produced by the exhaust of automobiles and power plants. Exposure to even low concentration of NO2 results in several skin and respiratory diseases, so highly selective and sensitive gas sensors are required to detect the presence of ppm level of NO2.The emerged two-dimensional (2D) materials have gained considerable attention in chemical sensing owing to its naturally high surface–to-volume ratio. However, the poor response time and incomplete recovery at room temperature remain a challenge to develop high-performance practical gas sensor. Herein, we report ultrafast detection and reversible MoS2 gas sensor at room temperature. The sensor’s performance was investigated to NO2 at room temperature and under thermal as well as photo energy. Incomplete recovery and high response time ~249 sec of sensor were observed at room temperature. Thermal energy was enough to complete recovery but it was at the expense of sensitivity. Further, under photo excitation, MoS2 exhibited an increment in response with ultrafast response time of ~29 sec and excellent recovery to NO2 (100ppm) at room temperature. Moreover, sensor showed reliable selectivity toward NO2 against various other gases. These unprecedented results are discussed based on the degree of charge perturbation on the surface of sensing layer in the context of NO2 /MoS2 interaction under optical-illumination.

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PROF. N. VEERAIAH

Department of Physics, Acharya Nagarjuna University, Nagarjunanagar
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    In plasma display panels, a transparent insulating layer (possessing high dielectric breakdown voltage, dielectric constant ~15 over a broad temperature range, high transparency in the visible region and low thermal expansion coefficient) is necessary to introduce between the arrays of front electrodes. Earlier, PbO based glasses were being used for such applications. However, due environment hazards, ZnO based glasses which possess all the above mentioned characteristics are being extensively used in place of PbO based glasses. In this study we havepartially crystallized ZnO based glasses with different concentrations of Ta2O5/Nb2O5/ZrO2and studied their dielectric breakdown strength along with detailed dielectric properties over wide ranges of frequency and temperature. Initial characterization of the material by XRD, SEM and spectroscopic studies have revealed the presence multiple crystal phases that contain Ta/Nb/Zr ions. The lattice parameters, optical band gap and band structure of these crystal phases were evaluated using generalized gradient approximation (GGA). Using these results together with the optical transparency studies, we have identified the optimal concentrations of dopants to improve the insulating strength and optical transparency of the investigated ZnO based glass ceramics. The dielectric break down strength of the material is found be improved by many folds due to the crystallization with the above mentioned transition metal oxides. The results of these studies may be useful for considering these materials for the applications of these materials in PDP panels.

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PROF. SHIV PRASAD

IIT, Bombay, Mumbai
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    Zn ferrite in bulk is antiferromagnet with a Neel temperature of around 10 K. Hence it showed a paramagnetic behavior at room temperature. As these magnetic properties are of no great interest, this material was never studied substantially. However, things changed when it was realized that nano-particles and nano-crystalline thin films of Zn ferrite show ferrimagnetic order only when particle/ grain size lies in a narrow range. It was later realized that it is not only the grain sizes but deposition parameters also which can change the magnetic properties of these films. However, it is always found that if the grain sizes increase beyond a limit, the films start behaving like bulk becoming paramagnetic at room temperature. Our group at IIT Bombay has been studying these materials for over a decade. This talk would introduce the exciting properties of the Zinc ferrite nano-crystalline thin films including the ferromagnetic resonance properties.

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PROF. SIMONE PELI

IIT Kharagpur
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    Besides the equilibrium spectroscopies (Absorption Spectroscopy, X-ray Spectroscopy, Photoemission Spectroscopy etc.) that are able to detect the static properties of a material, the Ultrafast Optical Spectroscopy open a window on the relaxation dynamics of such properties from an excited state down to the equilibrium. The energy stored by the electrons with an optical laser pulse is transferred within the material through different channels: electron-electron interaction, electron-phonon interaction etc. This de-excitation happens on different time-scales for the different exchange-channels so that the physical contributions can be singularly decomposed. This unique approach, thanks to the growing laser technology, permits to unveil new information on the physical properties of a wide variety of systems. From the quantum materials to the thermomechanics at the nanoscale, I will give an overview on the results obtained in my scientific career and on the techniques exploited to get them.

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PROF. VIJAYA SRINIVASU VALLABHAPURAPU

University of South Africa, Pretoria, South Africa
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    Microwave polluted environment can be very dangerous for human life and in certain cases, depending on immunological conditions cancerogenic and neurological effects can occur in the body [1,2]. Controlling microwave pollution is possible by using selective microwave absorbers. In this context, novel materials which can absorb microwaves effectively are of great interest. Further if the microwave absorption property can be tunable with very low magnetic fields, then it is even more interesting and useful. In this context, I shall discuss about various emerging magnetic, multiferroic and superconducting materials which exhibit the low field microwave absorption (LFMA) phenomenon [3-5].


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