@article {44564, title = {Structural elucidation of NASICON (Na3Al2P3O12) based glass electrolyte materials: effective influence of boron and gallium}, journal = {RSC Advances}, volume = {8}, year = {2018}, pages = {14422-14433}, type = {Journal Article}, abstract = {

Understanding the conductivity variations induced by compositional changes in sodium super ionic conducting (NASICON) glass materials is highly relevant for applications such as solid electrolytes for sodium (Na) ion batteries. In the research reported in this paper, NASICON-based NCAP glass (Na2.8Ca0.1Al2P3O12) was selected as the parent glass. The present study demonstrates the changes in the Na+ ion conductivity of NCAP bulk glass with the substitution of boron (NCABP: Na2.8Ca0.1Al2B0.5P2.7O12) and gallium (NCAGP: Na2.8Ca0.1Al2Ga0.5P2.7O12) for phosphorus and the resulting structural variations found in the glass network. For a detailed structural analysis of NCAP, NCABP and NCAGP glasses, micro-Raman and magic angle spinning-nuclear magnetic resonance (MAS-NMR) spectroscopic techniques (for 31P, 27Al, 23Na, 11B and 71Ga nuclei) were used. The Raman spectrum revealed that the NCAP glass structure is more analogous to the AlPO4 mesoporous glass structure. The 31P MAS-NMR spectrum illustrated that the NCAP glass structure consists of a high concentration of Q0 (3Al) units, followed by Q0 (2Al) units. The 27Al MAS-NMR spectrum indicates that alumina exists at five different sites, which include AlO4 units surrounded by AlO6 units, Al(OP)4, Al(OP)5, Al(OAl)6 and Al(OP)6, in the NCAP glass structure. The 31P, 27Al and 11B MAS-NMR spectra of the NCABP glass revealed the absence of B{\textendash}O{\textendash}Al linkages and the presence of B3{\textendash}O{\textendash}B4{\textendash}O{\textendash}P4 linkages which further leads to the formation of borate and borophosphate domains. The 71Ga MAS-NMR spectrum suggests that gallium cations in the NCAGP glass compete with the alumina cations and occupy four (GaO4), five (GaO5) and six (GaO6) coordinated sites. The Raman spectrum of NCAGP glass indicates that sodium cations have also been substituted by gallium cations in the NCAP glass structure. From impedance analysis, the dc conductivity of the NCAP glass (\~{}3.13 {\texttimes} 10-8 S cm-1) is slightly decreased with the substitution of gallium (\~{}2.27 {\texttimes} 10-8 S cm-1) but considerably decreased with the substitution of boron (\~{}1.46 {\texttimes} 10-8 S cm-1). The variation in the conductivity values are described based on the structural changes of NCAP glass with the substitution of gallium and boron.

}, issn = {20462069}, doi = {10.1039/C8RA01676C}, author = {Allu, Amarnath R.}, editor = {Balaji, Sathravada} } @article {46747, title = {Elucidating the effect of CaF 2 on structure, biocompatibility and antibacterial properties of S53P4 glass}, journal = {Journal of Alloys and Compounds}, volume = {831}, year = {2020}, month = {AUG }, pages = {154704}, type = {Article}, abstract = {

The present work focuses on the synthesis and structural elucidation of fluoride containing bioactive glasses in the system (in mol\%) given by (53.86) SiO2\ {\textendash} (22.65) Na2O {\textendash} (21.77-x) CaO {\textendash} (1.72) P2O5\ {\textendash} x CaF2, where, x\ =\ 0, 5.44, 10.885 and 16.33. The role of the incorporated fluoride and its distribution within the glass were interpreted and analyzed using Molecular dynamics (MD) simulations and the results were compared with the modified random network (MRN) model. The interpretations from the model have been verified using the MAS-NMR spectroscopy technique. According to this model, fluoride containing bioactive glasses have been proposed to consist of silicate rich network regions and modifier cation {\textendash} fluoride rich inter-network regions. The interface region was found to consist of non-bridging oxygen species (NBO) and phosphate cations which are either isolated orthophosphates (Q0P) or bridged with silicates in the form of pyrophosphate (Q1P) units forming Si{\textendash}O{\textendash}P bonds. The gradual substitution of CaF2\ for CaO in the base glass resulted in an increase in the silicate network connectivity with a reduction in the NBOs and lead to an increase in the association of modifier cations with fluoride ions. However, fluoride ions were found to show a marginal preference to associate with Na+\ cations leading to a decrease in the association of Na+\ ions with orthophosphate and silicate units. These overall structural findings were correlated with the\ in\ vitro\ ion dissolution behaviour of the bioactive glasses as well as with the thermal properties. The glasses were tested for their\ in\ vitro\ cell viability towards mouse osteoblast type (MC3T3) cells in which fluoride containing bioactive glasses did not show any toxicity and exhibited better cell proliferation. The antibacterial efficacy of the fluoride containing glasses was tested at various concentrations (5, 10 and 20\ mg/ml) in\ E.coli\ bacterial inoculum in which bactericidal action was evidenced.

}, keywords = {Fluoride bioactive glasses, In~vitro apatite formation and bactericidal action, MAS-NMR spectroscopy, MD simulations}, issn = {0925-8388}, doi = {10.1016/j.jallcom.2020.154704}, author = {Prasad, Sakthi and Ganisetti, Sudheer and Jana, Anuradha and Kant, Shashi and Sinha, P. K. and Tripathy, Sucheta and Illath, Kavya and Ajithkumar, T. G. and Annapurna, K. and Allu, Amarnath R. and Biswas, Kaushik} } @article {47736, title = {Elucidating the effect of CaF2 on structure, biocompatibility and antibacterial properties of S53P4 glass (vol 831, 154704, 2020)}, journal = {Journal of Alloys and Compounds}, volume = {883}, year = {2021}, month = {NOV}, pages = {161253}, type = {Correction}, issn = {0925-8388}, doi = {10.1016/j.jallcom.2021.161253}, author = {Prasad, Sakthi and Ganisetti, Sudheer and Jana, Anuradha and Kant, Shashi and Sinha, P. K. and Tripathy, Sucheta and Illath, Kavya and Ajithkumar, T. G. and Annapurna, K. and Allu, Amarnath R. and Biswas, Kaushik} } @article {47751, title = {Ionic conductivity of Na3Al2P3O12 glass electrolytes role of charge compensators}, journal = {Inorganic Chemistry}, volume = {60}, year = {2021}, month = {SEP }, pages = {12893-12905}, type = {Article}, abstract = {In glasses, a sodium ion (Na+) is a significant mobile cation that takes up a dual role, that is, as a charge compensator and also as a network modifier. As a network modifier, Na+ cations modify the structural distributions and create nonbridging oxygens. As a charge compensator, Na+ cations provide imbalanced charge for oxygen that is linked between two network-forming tetrahedra. However, the factors controlling the mobility of Na+ ions in glasses, which in turn affects the ionic conductivity, remain unclear. In the current work, using high-fidelity experiments and atomistic simulations, we demonstrate that the ionic conductivity of the Na3Al2P3O12 (Si0) glass material is dependent not only on the concentration of Na+ charge carriers but also on the number of charge-compensated oxygens within its first coordination sphere. To investigate, we chose a series of glasses formulated by the substitution of Si for P in Si0 glass based on the hypothesis that Si substitution in the presence of Na+ cations increases the number of SiOAl bonds, which enhances the role of Na as a charge compensator. The structural and conductivity properties of bulk glass materials are evaluated by molecular dynamics (MD) simulations, magic angle spinning-nuclear magnetic resonance, Raman spectroscopy, and impedance spectroscopy. We observe that the increasing number of charge-imbalanced bridging oxygens (BOs) with the substitution of Si for P in Si0 glass enhances the ionic conductivity by an order of magnitudefrom 3.7 x 10(-8) S.cm(-1) to 3.3 x 10(7) S.cm(-1) at 100 degrees C. By rigorously quantifying the channel regions in the glass structure, using MD simulations, we demonstrate that the enhanced ionic conductivity can be attributed to the increased connectivity of Na-rich channels because of the increased charge-compensated BOs around the Na atoms. Overall, this study provides new insights for designing next-generation glass-based electrolytes with superior ionic conductivity for Na-ion batteries}, issn = {0020-1669}, doi = {10.1021/acs.inorgchem.1c01280}, author = {Keshri, Shweta R. and Ganisetti, Sudheer and Kumar, Rajesh and Gaddam, Anuraag and Illath, Kavya and Ajithkumar, Thalasseril G. and Balaji, Sathravada and Annapurna, K. and Nasani, Narendar and Krishnan, N. M. Anoop and Allu, Amarnath R.} } @article {48229, title = {Elucidating the influence of structure and Ag+ -Na+ ion-exchange on crack-resistance and ionic conductivity of Na3Al1.8Si1.65 P-1.8 O-12 glass electrolyte}, journal = {Acta Materialia}, volume = {227}, year = {2022}, month = {APR }, pages = {117745}, type = {Article}, abstract = {

Glasses are emerging as promising and efficient solid electrolytes for all-solid-state sodium-ion batteries. However, they still suffer from poor ionic conductivity and crack-resistance, which need to be improved for better battery performance, reliability, and service life. The current study shows a significant enhancement in crack resistance (from 11.3 N to 32.9 N) for Na3Al (1.8) Si-1.65 P1.8O12 glass (Ag-0 glass) upon Na+ -Ag+ ion-exchange (IE) due to compressive stresses generated in the glass surface while the ionic conductivity values (similar to 10(-5) S/cm at 473 K) were retained. In this study, magic angle spinning-nuclear magnetic resonance (MAS-NMR), molecular dynamics (MD) simulations, Vickers micro hardness, and impedance spectroscopic techniques were used to evaluate the intermediate-range structure, atomic structure, crack resistance and conductivity of the glass. MAS-NMR and MD simulations confirm the presence of Si-OAl-O-P groups in the glass, thus enabling formation of Na percolated channel regions. AC-conductivity analysis for Ag-0 and ion-exchanged Ag-0 glass suggests that the mobility of Na+ ion increases with increasing temperature. It is observed that the measured mean square displacement (root \< R-2(t(p))\>) for sodium cations using AC-conductivity isotherms is nearly constant up to 448 K and then increases with increasing temperature up to 523 K. From the impedance spectra for ion-exchanged Ag-0 glass, it is identified that the increase in root \< R-2 (t(nu))\> and thereby, the mobility of sodium-ions for Ag-0 glass is due to the structural variations in the Ag-0 glass with increasing the temperature. Overall, the mechanisms presented in this article helps in formulating better glass based electrolyte materials for room temperature or high temperature sodium-ion batteries. (C) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

}, keywords = {amorphous, Ion-exchange, Ionic-conductivity, MD simulations, Mechanical property}, issn = {1359-6454}, doi = {10.1016/j.actamat.2022.117745}, author = {Keshri, Shweta R. and Mandal, Indrajeet and Ganisetti, Sudheer and Kasimuthumaniyan, S. and Kumar, Rajesh and Gaddam, Anuraag and Shelke, Ankita and Ajithkumar, Thalasseril G. and Gosvami, Nitya Nand and Krishnan, N. M. Anoop and Allu, Amarnath R.} }