Swarup Kundu
@sssihl.edu.in
Department of Physics
Sri Sathya Sai Institute of Higher Learning
Scopus Publications
Scopus Publications
Krisanta Rai and Swarup Kundu
IOP Publishing
Abstract LiZr2(PO4)3 (LZP) solid electrolyte shows excellent stability with Li metal anode and other electrode materials but suffers due to poor ionic conductivity at ambient temperatures. It synthesizes as a low conducting (10−8 S cm−1) triclinic phase at room temperature (RT), which undergoes a phase transition to a high conducting (10−5 S cm−1) rhombohedral phase at around 60 °C. Partial substitution of Zr4+ in LZP with La3+, Sr3+, Al3+, etc. is found to stabilize this high conducting phase at RT. In this work, rhombohedral phase stabilized LZP samples are prepared via the method of rapid cooling, wherein the samples are sintered at high temperatures for relatively short durations of time followed by rapid cooling/quenching to RT. Sample properties are characterized using XRD, SEM, and impedance spectroscopy (IS) techniques. Pristine LZP which was quenched to RT after sintering for 1200 °C/5h exhibited a high RT ionic conductivity value of 0.9 × 10−5 S cm−1. This high ionic conductivity value for pristine LZP has never been reported before. Pristine LZP is mostly found to possess ionic conductivity value in the range of 10−8–10−7 S cm−1 at RT.
Nishant Kumar Kolli, Dhivyaa Anandan, Amit Kumar Jaiswal, Swarup Kundu, and Santanu Roy
Springer Science and Business Media LLC
Nishant Kumar Kolli, Swarup Kundu, and Santanu Roy
Walter de Gruyter GmbH
Abstract The field of biomaterials continually seeks novel materials to meet the requirements of bone tissue engineering. This manuscript explores polyvinyl alcohol (PVA)–combeite composites. The composites were characterized using X-ray diffraction and scanning electron microscopy. Notably, the X-ray diffraction patterns unveil a combination of amorphous and crystalline regions attributed to PVA and combeite, respectively. More importantly, PVA–combeite composites exhibit reduced swelling and degradation rates compared to pure PVA. The percentage swelling and degradation values (%) for the prepared materials fall within the range of 190–340 and 55–75, respectively. The spherical apatite structures formed post the immersion in Hanks’ Balanced Salt Solution indicate that these materials could be used in the field of bone tissue engineering.
Nishant Kumar Kolli, Swarup Kundu, and Santanu Roy
Springer Science and Business Media LLC
Krisanta Rai and Swarup Kundu
Elsevier BV
Nishant Kumar Kolli, Datta Darshan V M, Dhivyaa Anandan, Venketesh Sivaramakrishnan, Amit Kumar Jaiswal, Siva Kumar Belliraj, Swarup Kundu, and Santanu Roy
IOP Publishing
Abstract Silicate ceramics are one of the established candidates employed in many industrial and medical applications. Not many of the existing reports mention and investigate the properties of the phases or individual components of these materials. In this exploratory study, one such sodium calcium silicate, combeite (Na2Ca2Si3O9) was synthesized by the solid-state route and studied for its properties. The preliminary investigation involved thermal treatments followed by characterization to identify the formation of the pure phase. The mechanical behaviour was evaluated by compression tests. Surface treatments were executed to enhance the capabilities to support cellular proliferation. The in-vitro acellular immersion test showed the formation of calcium phosphates. All the tested materials exhibited adequate cell viability properties for prospective applications in life sciences.
Nishant Kumar Kolli, Sai Phalguna Kanikaram, Krisanta Rai, Swarup Kundu, and Santanu Roy
IOP Publishing
Abstract The current study combeite (Na2Ca2Si3O9) was synthesized by the sol-gel route and an attempt was made to investigate its various features. The formation of a pure phase was confirmed using the powder x-ray diffraction technique. Dielectric measurements were performed on the synthesized material over a wide range of temperature and frequency. The optical band gaps were found to be in the range 1.5–2.8 eV. The in-vitro acellular immersion studies showed the formation of apatite on the surface of combeite. The cell proliferation assay indicated enhanced cell viability in the case of combeite when compared to calcium phosphate. These results of this study have implications for various industrial and medical applications.
Rajasekhar Bhimireddi, Sai Pavan Prashanth Sadhu, Lokeswararao Dhavala, Tukaram Shet, Swarup Kundu, Anees A. Ansari, M. Aslam Manthrammel, and S. AlFaify
Elsevier BV
K.I. Chatzipanagis, N.S. Tagiara, D. Möncke, S. Kundu, A.C.M. Rodrigues, and E.I. Kamitsos
Elsevier BV
P. S. J. Bharadwaj, Swarup Kundu, Vijay Sai Kollipara, and Kalidindi B. R. Varma
Royal Society of Chemistry (RSC)
The work investigates the impact of doping (Sm3+, Gd3+ at Y3+ site and Ti4+ at Fe3+ site respectively) on structural, optical and magnetic properties of YFeO3.
P S J Bharadwaj, Swarup Kundu, Vijay Sai Kollipara, and Kalidindi B R Varma
IOP Publishing
Fine powders of Y1−xSmxFeO3 (x = 0, 0.05, 0.10, 0.15) were synthesized via citrate based sol–gel route. While the as synthesized powders were amorphous, the calcined (900 °C/8 h) powders were confirmed to be polycrystalline by x-ray powder diffraction (XRD) studies. The calcined powders were found to crystallize in an orthorhombic structure associated with the lattice parameters a = 5.59 Å, b = 7.60 Å, c = 5.28 Å. These lattice parameters increased with the increase in Sm3+ content at yttrium sites. The strain that was obtained by the Williamson–Hall method increased with the increase in dopant (Sm3+) concentration vis-à-vis a decrease in crystallite size. Diffuse reflectance spectroscopic studies suggest an increase in band gap as Sm doping level increased. Significant enhancement in magnetization associated with a decrease in coercive field accompanied by a transition from anti-ferromagnetic to soft ferromagnetic behaviour in Sm doped YFeO3 were encountered. It is hoped that these materials with the enhanced magnetic properties could be of potential use for multifarious applications.
Rafael A. C. Amoresi, Leonélio Cichetto, Swarup Kundu, Marcio D. Teodoro, Gilmar E. Marques, Elson Longo, Juan Andrés, Adenilson J. Chiquito, and Maria A. Zaghete
AIP Publishing
Two-dimensional electron gas (2DEG) in SrTiO3/LaAlO3 heterostructures has been extensively studied in the last few years; however, little attention has been given to a practical way to contact electrically the low dimensional gas at the interface. This work demonstrates a method to contact the 2DEG formed at the oxide interfaces connected by platinum electrodes which were made by the decomposition of organometallic gas using focused ion beams. On the surface, the electrodes were defined through photolithography, and at the interface, the electrodes were deposited through the focused ion beams and electrons, which were then evaluated. The quality of the interface electrodes was evaluated at two different partial oxygen pressures (pO2) used for the film deposition: low (10−4 mbar) and high (10−1 mbar). The electrode deposition conditions using electrons or ions have resulted in different rates of metal deposition and interaction with the interface leading to either metallic (2DEG) or insulating behavior.Two-dimensional electron gas (2DEG) in SrTiO3/LaAlO3 heterostructures has been extensively studied in the last few years; however, little attention has been given to a practical way to contact electrically the low dimensional gas at the interface. This work demonstrates a method to contact the 2DEG formed at the oxide interfaces connected by platinum electrodes which were made by the decomposition of organometallic gas using focused ion beams. On the surface, the electrodes were defined through photolithography, and at the interface, the electrodes were deposited through the focused ion beams and electrons, which were then evaluated. The quality of the interface electrodes was evaluated at two different partial oxygen pressures (pO2) used for the film deposition: low (10−4 mbar) and high (10−1 mbar). The electrode deposition conditions using electrons or ions have resulted in different rates of metal deposition and interaction with the interface leading to either metallic (2DEG) or insulating behavior.
Shiv Prakash Singh, José Fabián Schneider, Swarup Kundu, Ana Candida Martins Rodrigues, Paulo Parreira Gomes de Mattos, Edgar Dutra Zanotto, Jean Rocherullé, Patricia Bénard-Rocherullé, and Ronan Lebullenger
Elsevier BV
Marcos de Oliveira, Janete Schultz Oliveira, Swarup Kundu, Norma Maria Pereira Machado, Ana Candida M. Rodrigues, and Hellmut Eckert
Elsevier BV
Jefferson Esquina Tsuchida, Fabio Aparecido Ferri, Paulo Sergio Pizani, Ana Candida Martins Rodrigues, Swarup Kundu, José Fabián Schneider, and Edgar Dutra Zanotto
Royal Society of Chemistry (RSC)
Experimental evidence has confirmed that the mixed-ion effect (MIE) can be explained as a natural consequence of random ion mixing and that the cation size mismatch is not the only factor that determines the intensity of MIE.
Silvia H. Santagneli, Helio V. A. Baldacim, Sidney J. L. Ribeiro, Swarup Kundu, Ana Candida Martins Rodrigues, Carsten Doerenkamp, and Hellmut Eckert
American Chemical Society (ACS)
Highly ion conducting glass-ceramics, crystallizing in the Na-superionic conducting (NASICON) structure, have been prepared in the system Li1+xAlxSnyGe2-(x+y)(PO4)3 by crystallization of glassy precursor samples. For modest substitution levels (y = 0.25), these crystalline solid solutions show slightly higher electrical conductivity than corresponding samples without Sn, supporting the rationale that the lattice expansion associated with the substitution of Ge by its larger homologue Sn can enhance ionic conductivity. Higher Sn substitution levels (y = 0.45) do not result in any improvement. The glass-to-crystal transition has been characterized in detail by multinuclear single and double resonance NMR experiments. While substantial changes in the 31P and 27Al MAS NMR spectra indicate that the crystallization of the glasses is accompanied by significant modifications in the local environments of the phosphate and the aluminum species, the dipolar solid state NMR experiments indicate that the structures of...
Shivanand Madolappa, Swarup Kundu, Rajasekhar Bhimireddi, and K B R Varma
IOP Publishing
Ceramics of Bi1−xPrxFeO3 (x = 0–0.1) were fabricated using the nanocrystalline powders obtained via sol–gel route. X-ray powder diffraction studies confirmed that these belonged to rhombohedral perovskite structure associated with R3c space group. The dielectric properties of the ceramic samples as a function of frequency (100 Hz–10 MHz) and temperature (30 °C–250 °C) were studied. The dielectric constant increased while the loss decreased with the increase of Pr content. Dielectric dispersion in these samples was found to be poly dispersive Debye type relaxation as confirmed by invoking Cole–Cole relation. Impedance spectroscopy was employed to determine the electrical parameters associated with the grain and grain boundaries. Grain and grain boundary resistances were found to decrease with the increase of temperature for all the samples under study. The activation energies for the dielectric relaxation were evaluated by electric modulus spectra and these increase with the increase of Pr dopant level. The frequency dependent conductivity at various temperatures demonstrated the involvement of correlated barrier hopping conduction mechanism. The electrical conduction in these ceramics was ascribed to long and short range migration of oxygen ion vacancies as demonstrated by temperature dependent ac conductivity studies.
Swarup Kundu, Rajasekhar Bhimireddi, Kavita Mishra, S B Rai, and K B R Varma
IOP Publishing
The present work deals with the structural and efficient down-shifting (DS) and up-conversion (UC) luminescence properties of erbium ion (Er3+) doped nanocrystalline barium sodium niobate (Ba2Na1−3xErxNb5O15, where x = 0, 0.02, 0.04 and 0.06) powders synthesized via novel citrate-based sol-gel route. The monophasic nature of the title compound was confirmed via x-ray powder diffraction followed by FT-IR studies. High-resolution transmission electron microscopy (HRTEM) facilitated the establishment of the nanocrystalline phase and the morphology of the crystallites. The Kubelka–Munk function, based on diffused reflectance studies and carried out on nano-sized crystallites, was employed to obtain the optical band-gap. The synthesized nanophosphor showed efficient DS/PL-photoluminescence and UC luminescence properties, which have not yet been reported so far in this material. The material emits intense DS green emission on excitation with 378 nm radiation. Interestingly, the material gives intense UC emission in the visible region dominated by green emission and relatively weak red emission on 976 nm excitation (NIR laser excitation). Such a dual-mode emitting nanophosphor could be very useful in display devices and for many other applications.
Satyanarayan Patel, Aditya Chauhan, Swarup Kundu, Niyaz Ahamad Madhar, Bouraoui Ilahi, Rahul Vaish, and K. B. R. Varma
AIP Publishing
This study systematically investigates the phenomenon of internal clamping in ferroelectric materials through the formation of glass-ceramic composites. Lead-free 0.715Bi(0.5)Na(0.5)TiO(3)-0.065BaTiO(3)-0.22SrTiO(3) (BNT-BT-ST) bulk ferroelectric ceramic was selected for the course of investigation. 3BaO - 3TiO(2) - B2O3 (BTBO) glass was then incorporated systematically to create sintered samples containing 0%, 2%, 4% and 6% glass (by weight). Upon glass induction features like remnant polarization, saturation polarization, hysteresis losses and coercive field could be varied as a function of glass content. Such effects were observed to benefit derived applications like enhanced energy storage density similar to 174 k J/m(3) to similar to 203 k J/m(3) and pyroelectric coefficient 5.7x10(-4) Cm-2K-1 to 6.8x10(-4) Cm-2K-1 by incorporation of 4% glass. Additionally, BNT-BT-ST depolarization temperature decreased from 457K to 431K by addition of 4% glass content. Glass incorporation could systematically increases diffuse phase transition and relaxor behavior temperature range from 70 K to 81K and 20K to 34 K, respectively when 6% and 4% glass content is added which indicates addition of glass provides better temperature stability. The most promising feature was observed to be that of dielectric response tuning. It can be also used to control (to an extent) the dielectric behavior of the host ceramic. Dielectric permittivity and losses decreased from 1278 to 705 and 0.109 to 0.107 for 6% glass, at room temperature. However this reduction in dielectric constant and loss increases pyroelectric figures of merit (FOMs) for high voltage responsivity (F-v) high detectivity (F-d) and energy harvesting (F-e) from 0.018 to 0.037 m(2)C(-1), 5.89 to 8.85 mu Pa-1/2 and 28.71 to 61.55 Jm(-3)K(-2), respectively for 4% added ceramic-glass at room temperature. Such findings can have huge implications in the field of tailoring ferroelectric response for application specific requirements. (C) 2015 Author(s).
Swarup Kundu and Kalidindi B. R. Varma
Wiley
The temperature (300-973K) and frequency (100Hz-10MHz) response of the dielectric and impedance characteristics of 2BaO-0.5Na(2)O-2.5Nb(2)O(5)-4.5B(2)O(3) glasses and glass nanocrystal composites were studied. The dielectric constant of the glass was found to be almost independent of frequency (100Hz-10MHz) and temperature (300-600K). The temperature coefficient of dielectric constant was 8 +/- 3ppm/K in the 300-600K temperature range. The relaxation and conduction phenomena were rationalized using modulus formalism and universal AC conductivity exponential power law, respectively. The observed relaxation behavior was found to be thermally activated. The complex impedance data were fitted using the least square method. Dispersion of Barium Sodium Niobate (BNN) phase at nanoscale in a glass matrix resulted in the formation of space charge around crystal-glass interface, leading to a high value of effective dielectric constant especially for the samples heat-treated at higher temperatures. The fabricated glass nanocrystal composites exhibited P versus E hysteresis loops at room temperature and the remnant polarization (P-r) increased with the increase in crystallite size.
Swarup Kundu and K. B. R. Varma
American Chemical Society (ACS)
Monophasic Ba2NaNb5O15 was crystallized at nanometer scale (12–36 nm) in 2BaO–0.5Na2O–2.5Nb2O5–4.5B2O3 glass system. To begin with, optically transparent glasses, in this system, were fabricated via the conventional melt-quenching technique. The amorphous and glassy characteristics of the as-quenched samples were respectively confirmed by X-ray powder diffraction and differential thermal analyses. Nearly homogeneous distribution of Ba2NaNb5O15 (BNN) nanocrystals associated with tungsten bronze structure akin to their bulk parent structure was accomplished by subjecting the as-fabricated glasses to appropriate heat-treatment temperatures. Indeed transmission electron microscopy (TEM) carried out on these samples corroborated the presence of Ba2NaNb5O15 nanocrystals dispersed in a continuous glass matrix. The as-quenched glasses were ∼75% transparent in the visible range of the electromagnetic spectrum. The optical band gap and refractive index were found to have crystallite size (at nanoscale) dependence. ...
Ashutosh K. Dubey, P.K. Mallik, S. Kundu, and B. Basu
Elsevier BV
Swarup Kundu and K. B. R. Varma
Royal Society of Chemistry (RSC)
Fine powders comprising nanocrystallites of barium sodium niobate, Ba2NaNb5O15 (BNN) were obtained via a citrate assisted sol–gel route at a much lower temperature than that of the conventional solid-state reaction route. The phase evolution of BNN as a function of temperature was investigated by thermogravimetric analysis (TGA), differential thermal analysis (DTA), Fourier transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD). DTA data followed by XRD studies confirmed the BNN formation temperature to be around 923 K. The as-synthesized powders heat-treated at 923 K/10 h attained an orthorhombic structure akin to that of the parent BNN phase. Transmission electron microscopy revealed that the nanocrystallites are associated with dislocations. The optical band gap was calculated using the Kubelka–Munk function. These nanocrystallites exhibited strong visible photoluminescence (PL) at room temperature. The PL mechanism was explained by invoking the dielectric confinement effect, defect states and generation of self-trapped excitons.
Sunil Kumar, Swarup Kundu, D.A. Ochoa, J.E. Garcia, and K.B.R. Varma
Elsevier BV