Department of Physics
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Item Thermal Investigation on Mechanically Milled and Melt - Quenched Superionic Glasses(Indian Association for the Cultivation of Science, 2005) Dalvi, AnshumanItem Electrical transport in superionic thin films prepared by pulsed laser deposition(AIP, 2011) Dalvi, AnshumanSuperionic thin films are obtained using PLD technique from ion oxysalt glassy target. The structural and electrical properties of the films have been investigated. Partially amorphous nature of the films has been confirmed by X‐ray diffraction measurements. The electrical conductivity of the sample has been measured at well controlled heating rate of Conductivity temperature cycles suggest that deposited films are essentially ionic in nature.Item Electrical transport and structural investigations in Cu2O substituted AgI-Ag2O-V2O5 glass-ceramic nanocomposites(AIP, 2012-06) Dalvi, AnshumanGlass-ceramic nanocomposites in Cu2O substituted AgI-(Ag2O)1-x-(Cu2O)x-V2O5 superionic system are prepared by annealing the melt-quenched glasses above the crystallization temperatures. Structural and electrical properties have been investigated. Scanning electron microscopy suggests the existence of fine particles of size 20-200 nm dispersed in the annealed glass matrix. Samples are essentially ionic and stable under conductivity-temperature cycles upto ∼ 160 °C. It is found that the conductivity in the nanocomposites increases with Cu2O substitution and highest conductivity is found to be ∼ 2 × 10−3 Ω−1cm−1 for x = 0.3 at room temperature. Differential scanning calorimetry scans confirm the existence of silver iodide crystallites in all the glass-ceramic compositions.Item Climate justice is central to addressing the climate emergency’s psychological consequences in the Global South: a narrative review(CUP, 2013-09) Dalvi, AnshumanWe present neutron diffraction results on superionic materials that are good candidates for use as solid-state electrolytes in next generation Li+ ion batteries. Lithium ion conducting glasses of the compositions xLi2SO4-(1-x) [0.5Li2O-0.5(2NH4H2PO2)] ; x=0 and 0.1 were synthesized by conventional melt-quenching. The transparent homogeneous glassy flakes were thus obtained and used for the characterization. The materials are glassy in nature and composed of a complex network of the following sub-units: Li2O, Li2SO4, and 2NH4H2PO2. This disordered structure is integral to its function in that it promotes Li+ ion conduction while suppressing electronic conduction, the necessary qualities of a good Li+ electrolyte. We used neutron diffraction to study the formation of crystallites upon heating of the material above 400°C. The crystallite formation is understood to be detrimental to the Li+ ion mobility and, hence, is identified with a diminished performance in devices that require heating in their fabrication processs. Here, we report the changes in the material, as observed by neutron diffraction, as a function of annealing temperature and temperature history.Item Neutron Scattering Studies of Glassy Solid-State Lithium Ion Based Electrolytes(CUP, 2013-09) Dalvi, AnshumanWe present neutron diffraction results on superionic materials that are good candidates for use as solid-state electrolytes in next generation Li+ ion batteries. Lithium ion conducting glasses of the compositions xLi2SO4-(1-x) [0.5Li2O-0.5(2NH4H2PO2)] ; x=0 and 0.1 were synthesized by conventional melt-quenching. The transparent homogeneous glassy flakes were thus obtained and used for the characterization. The materials are glassy in nature and composed of a complex network of the following sub-units: Li2O, Li2SO4, and 2NH4H2PO2. This disordered structure is integral to its function in that it promotes Li+ ion conduction while suppressing electronic conduction, the necessary qualities of a good Li+ electrolyte. We used neutron diffraction to study the formation of crystallites upon heating of the material above 400°C. The crystallite formation is understood to be detrimental to the Li+ ion mobility and, hence, is identified with a diminished performance in devices that require heating in their fabrication processs. Here, we report the changes in the material, as observed by neutron diffraction, as a function of annealing temperature and temperature history.Item Neutron scattering studies of glassy Li+ superionics(American Physical Society, 2013-03) Dalvi, AnshumanTwo distinct neutron scattering techniques were implemented in the study of glassy superionic materials composed of a complex network of their interconnected sub-units: Li2O, NH4H2PO2, and Li2SO4. The use of disordered materials underlies an effort to promote Li+ mobility, while suppressing e- conductivity, which makes them good candidates for use as electrolytes in lithium ion batteries. We present triple-axis spectrometer results of energy resolved vs. energy integrated neutron scattering that indicate the presence of a broad range of dynamic processes in the materials, rather than well-defined excitations. Additionally, we report on neutron diffraction data that demonstrates the formation of crystallites within the material upon annealing up to 450 °C. Such crystallites hinder the performance of the materials as electrolytes, which is evident in thin film devices where heating is unavoidable during fabrication.Item Li2SO4-Li2O-P2O5 Ionic glass dispersed with [Bmim] [PF6] ionic liquid: Electrical transport and thermal stability investigations(AIP, 2014-04) Dalvi, AnshumanA fast ionic composite is prepared by dispersion of Ionic liquid [Bmim][PF6] in glass matrix by mixing and through grinding. Amorphous/glassy nature of the samples is confirmed by X-Ray diffraction (XRD). Surprisingly, the electrical conductivity of the samples is found to be increasing by ∼ 2 orders of magnitude and exhibits typical Arrhenius behavior with low activation energy. DC polarization and impedance spectroscopy measurements suggest that samples are essentially ionic in nature. The conductivity isotherms were also obtained at different temperatures (T < 100 °C) and found to be appreciably stable at least for ∼ 10 days.Item Li{sub 2}SO{sub 4}−Li{sub 2}O−P{sub 2}O{sub 5} ionic glass dispersed with [Bmim] [PF{sub 6}] ionic liquid: Electrical transport and thermal stability investigations(Office of Scientific and Technical Information, 2014) Dalvi, AnshumanA fast ionic composite is prepared by dispersion of Ionic liquid [Bmim][PF{sub 6}] in Li{sub 2}SO{sub 4}−Li{sub 2}O−P{sub 2}O{sub 5} glass matrix by mixing and through grinding. Amorphous/glassy nature of the samples is confirmed by X-Ray diffraction (XRD). Surprisingly, the electrical conductivity of the samples is found to be increasing by ∼ 2 orders of magnitude and exhibits typical Arrhenius behavior with low activation energy. DC polarization and impedance spectroscopy measurements suggest that samples are essentially ionic in nature. The conductivity isotherms were also obtained at different temperatures (T < 100 °C) and found to be appreciably stable at least for ∼ 10 days.Item Li+ ion NASICON-glass-ceramics prepared by milling assisted synthesis route: assessment of structure and enhanced electrical transport(International Atomic Energy Agency, 2018-12) Dalvi, AnshumanPresent work reveals some interesting findings on Li+ ion conducting glass-ceramics prepared by a novel external dispersion route. Our recent investigations on two interesting aspects, viz. (i) Li+ ion glass dispersion in NASICON, and (ii) Li+-NASICON dispersion in an ionic glass reveal interesting results. Li+ ion conducting analogues of NASICON, viz. Li+Ti2(PO4)3 known as LTP exhibit in grain conductivity as high as 104Ω-1cm-1, however their application is limited due to high grain boundary impedance (GBI) that limits the conductivity to 10-7-10-8Ω-1cm-1. It has been demonstrated that the GBI can be tailored appreciably by incorporating highly conducting glassy phase at the grain interfaceItem Novel LTP-glass-ceramic nanocomposites: assessment of electrical transport and structure(International Atomic Energy Agency, 2018) Dalvi, AnshumanThese have been found to be significantly higher than that of the pristine LTP prepared with similar preparation conditions. Addition of glass-ceramic in LTP matrix leads to improvement in thermal activation of the composite at ambient temperatures, as suggested by dissipation factor trend. These composites exhibit better density than pristine LTP samples. Energy dispersive X-Ray spectroscopy (EDS) mapping on fractured surface confirms homogeneous elemental distribution. Cyclic Voltammetry (CV) results suggest that these composites are potential candidates for solid state battery applications