Faculty Publications
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Item Sodium ion incorporated alumina - A versatile anisotropic ceramic(Elsevier Ltd, 2019) Pujar, P.; Gupta, B.; Sengupta, P.; Gupta, D.; Mandal, S.The present article is a review of crystal structure dependent anisotropic properties of β and β″-phases of sodium ion incorporated alumina. The anisotropy in electrical properties such as ionic conductivity and dielectric permittivity is due to the layered structure. Conducting plane between two consecutive spinel aluminas constituting loosely bound mobile sodium ions, promote ionic conductivity in the parallel direction. In contrary, the restricted movement of ions in the orthogonal direction brings about polarization giving it directional dielectric property. High ionic conductivity of 1.3 S/cm and large dielectric constant of ˜ 200 are reported. Exchanging sodium ions with different cations, such as potassium and lithium, results in similar anisotropy. The processing of β and β″-phases along with metastability of intermediate mullite phase is described in the current review. In addition, the applications of sodium ion incorporated aluminas, such as solid electrolyte in batteries, thin film transistors and gas sensors are discussed. © 2019 Elsevier LtdItem A revisit to solution-processed zirconia and its stabilized derivatives as protective coatings for base-stainless steel(Taylor and Francis Ltd., 2023) Vardhan, R.; Eknath Chaudhari, N.; Pujar, P.; Mandal, S.Stainless steel (SS) is a well-known engineering material which is predominantly used in multitudinous applications; however, the disquieting entity is its deteriorative nature triggered by the corrosion in biological, chemical, and high-temperature surroundings. Zirconia is a noteworthy material because of its remarkable mechanical, thermal, and biocompatible properties. To further improve the properties, the high-temperature phases of zirconia are stabilized at room temperature. Zirconia and its stabilized derivates are favored candidates as protective coatings for SS. They offer high resistance, allow them to perform in corrosive, sensitive environments, and augment the longevity, serviceability of SS. Deposition of zirconia/stabilized-zirconia (Z/s-Z) coatings is accomplished using vapor-phase methods, which are capital-intensive; they comprise high vacuum and processing time, confined space, and more energy consumption, resulting in fabrication cost maximization. Alternatively, solution-phase deposition methods are advantageous, effortless, and capable of depositing on large-area substrates, promising to lessen fabrication costs and to enhance yield. Solution-phase methods, namely dip, spray, and spin coatings, have been investigated to produce effective, high-grade Z/s-Z coatings on SS. This review summarizes the utilized precursors, solvents, and process parameters for depositing Z/s-Z coatings on different types and grades of steel through mentioned solution-phase methods, respectively. The review emphasizes the researched potential applications of solution-phase processed Z/s-Z with a particular role as a protective coating on SS-based implants, surgical instruments preserving corrosion resistance, nontoxicity and biocompatibility in the body fluids. The review also highlights the defensive property of solution-phase processed Z/s-Z coatings to the underneath SS against corrosive chemical media (acids like H2SO4, HCl, HNO3; chlorides like NaCl and toxic gases like H2S, coal). The oxidation protection to the beneath SS by the mentioned coatings in aggressive high-temperature surroundings is also focused in the present review. © 2022 Taylor & Francis Group, LLC.Item Development of low temperature stoichiometric solution combustion derived transparent conductive ternary zinc tin co-doped indium oxide electrodes(Royal Society of Chemistry, 2017) Pujar, P.; Gandla, S.; Singh, M.; Gupta, B.; Tarafder, K.; Gupta, D.; Noh, Y.-Y.; Mandal, S.Here, the development of transparent conductive zinc tin co-doped indium oxide (IZTO: In1.4Sn0.3Zn0.3O3) ternary electrodes is addressed through low temperature solution combustion processing. Optimization of fuel to oxidizer ratio offers low temperature (?130 °C) of combustion with balanced redox reaction. The thin films of IZTO annealed at different temperatures showed a decreasing trend in the resistivity with a fixed order of 10-2 ? cm and the film with a highest Hall mobility of 5.92 cm2 V-1 s-1 resulted at 400 °C. All the films with different temperatures of annealing were smooth (rms ? 2.42 nm) in nature and the IZTO film annealed at 200 °C is 83% transparent in the visible spectra. The effective band gap of 0.9 eV determined from first-principles density functional theory gives clear evidence for the conducting nature of IZTO. The thin film transistor fabricated with IZTO as a gate electrode with poly(methyl methacrylate) and pentacene as the dielectric and channel material, respectively, exhibited a saturation mobility of 0.44 cm2 V-1 s-1 and Ion/Ioff ratio of 103. Further, the printability of the IZTO combustible precursor is established which resulted in anti-edge deposition of the printed feature. © 2017 The Royal Society of Chemistry.Item Retention of high dielectric constant sodium beta alumina via solution combustion: Role of aluminum ions complexation with fuel(Elsevier Ltd, 2018) Gupta, B.; Pujar, P.; Mal, S.S.; Gupta, D.; Mandal, S.In the present study, solution combustion technique has been explored to synthesize Sodium ?-alumina (SBA; NaAl11O17) powder and thin films. Three fuels namely urea, glycine and citric acid have been used to seek the feasibility of synthesizing crystalline SBA powder at low temperature. Also, the effect of nature of fuels used as well as calcination treatment on phase evolution and morphology of the as-combusted powder was investigated. Thermal analysis and X-ray diffraction studies suggest the formation of crystalline SBA powder at temperature as low as 259 °C, using urea in the combustion reaction whereas other fuels resulted in amorphous SBA phase and this variation in phase was found due to difference in exothermicity of the fuel used. Thermodynamic and spectroscopic analyses showed that the exothermicity of fuel depends on various factors like (i) standard heat of formation of fuel and (ii) the complexation offered by fuel to metal cations. Furthermore, sodium ?-alumina thin film capacitor (metal-insulator-metal) was also fabricated using urea via spray combustion synthesis. The sodium ?-alumina thin film showed a high dielectric value (?r) of ~21. © 2017 Elsevier Ltd and Techna Group S.r.l.Item A balancing between super transparency and conductivity of solution combustion derived titanium doped indium oxide: Effect of charge carrier density and mobility(Elsevier B.V., 2018) Pujar, P.; Vardhan, R.V.; Gupta, D.; Mandal, S.In this contribution, super transparent (~100%) and conducting In14Ti1O23 (Titanium doped Indium oxide; InTiO) films were reported via solution combustion processing with acetylacetone as fuel. Both bulk-powder and thin film systems were studied and revealed the efficacy of low temperature combustion synthesis which yielded crystalline InTiO powder at 150 °C and its film counterpart had shown pronounced crystalinity with temperature. Also, all films with varying annealing temperature were smooth with rms value ranging from 0.29 nm to 1.9 nm. In addition, the charge carrier density in all films found to be of the order 1019 cm?3, possessing highest transparency nearly equals to uncoated glass at an annealing temperature of 350 °C having maximum of ~67% metal-oxygen-metal framework (or lattice oxygen) confirmed via X-ray photoelectron spectroscopy. Also, the highest conductivity of 20 S/cm at an annealing temperature of 450 °C clearly conveyed the potential of solution combustion processing in the fabrication of ultra-transparent InTiO films with no sophistication in the film fabrication. © 2018Item Investigation of sintering kinetics and morphological evolution of silver films from nano-dispersion(Springer Verlag service@springer.de, 2018) Pujar, P.; Anusha, P.; Gupta, D.; Mandal, S.The present study aimed at investigating the sintering kinetics and the mechanism of achieving uniform film morphology from silver nano-dispersion through evaporation of the solvent. A tuned time elapse between drop casting of silver dispersion and the annealing (dwell-time) acted as the decision maker in engineering the morphology: ring stain (infinite dwell-time), uniform deposit (variable dwell-time) and dot formation (zero dwell-time). Three distinct dwell-times (10, 20 and 30 min) are chosen for the study at different temperatures (120 to 250 °C) and the conclusion is derived based on the profile of the deposit. The frozen morphology that resulted from the evaporation goes through the debonding of surfactant with simultaneous sintering to minimize the surface energy. A linear isothermal sintering model comprising initial grain size, grain growth parameter, annealing time and fractional porosity helps to predict the grain size post-annealing. Theoretical predictions of grain sizes are well matched with experimental ones. The grain growth parameter which shows an upward trend with the annealing temperature is mainly due to a reduction in the porosity and the increase in the fraction of solid–solid interface which shows betterment in the percolation paths available for the movement of carriers. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.Item Facile in situ formation of high conductive Ag and Cu x O y composite films: a role of aqueous spray combustion(Springer New York LLC barbara.b.bertram@gsk.com, 2019) Salian, A.; Pujar, P.; Mandal, S.In the present contribution, in situ formation of low-temperature high conductive composite films composed of pure silver and oxides of copper (Cu x O y where, x = y = 1 for CuO and x = 2, y = 1 for Cu 2 O), are presented through spray combustion with a balanced stoichiometric redox reaction. High electrical conductivity (~ 7.8 × 10 5 S/cm) was retained in the composite film at an annealing temperature of 170 °C with matrix silver phase being 50% by volume. Whereas electrical conductivity of spray combustion processed pure silver is found to be ~ 2 × 10 6 S/cm. In situ formation of the composite film directly from the silver and cupric nitrate aqueous precursor solution through spray combustion proves it to be compositionally tunable with minimal usage of noble metal. Presence of Ag and Cu x O y is confirmed by X-ray diffraction and X-ray photoelectron spectroscopy. The ratio of Cu 1+ /Cu 2+ in the composite is found to be 0.54 and 0.43 at an annealing temperature of 170 °C and 400 °C respectively. The transformation of Cu 2 O to CuO is highly a thermally activated phenomenon; as the vacancy driven electrical conductivity is more in Cu 2 O than CuO, stabilization of Cu 2 O at a lower temperature is desired. The composite electrode can have potential applications in optoelectronics, printed electronics and catalysis. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.Item High-performance low voltage operation of indium zinc tin oxide thin film transistors using chemically derived sodium ?-alumina dielectric(Springer, 2019) Pujar, P.; Gupta, D.; Mandal, S.We present high performance, low voltage (< 3 V) operation of thin film transistors (TFTs) with indium zinc tin oxide (IZTO: In4Sn4ZnO15)-semiconductor. The film of IZTO was fabricated via low-temperature (200 °C) solution combustion processing without incorporating an external fuel. As 2-methoxyethanol is a widely used organic solvent due to its high dissolution capability, serve the purpose of both the solvent and the fuel. On quantification from the balanced redox reaction, 0.3% of 2-methoxyethanol assisted for the action of fuel and helped in the formation of metal oxide, and the rest (99.7%) served the purpose of being dissolution medium. The balanced redox chemistry yielded a significant fraction of (56.5%) metal oxide at 200 °C confirmed via high-resolution oxygen 1 y spectrum. Further, the chemically derived thin film of sodium ss-alumina with a dielectric constant of ~ 21, while annealing at 350 °C incorporated in the TFT for the realization of low voltage operation. The performance assessment is systematically carried out both silicon dioxide (SiO2) and sodium ss-alumina and found that the TFTs with SiO2 and IZTO exhibited a saturation mobility (µ^), Ion/Ioff ratio and the threshold voltage (Vth) of 0.50 ± 0.02 cm2 V-1 s-1, 1.25 x 104 and 6.6 ± 0.79 V respectively. While changing the dielectric to sodium ss-alumina presented a µsat, Ion/Ioff ratio and Vth of 4.21 ± 0.18 cm2 V-1 s-1, 1.4 x 102 and 0.47 ± 0.08 V respectively. © Springer Science+Business Media, LLC, part of Springer Nature 2019.Item Low-temperature reducible particle-free screen-printable silver ink for the fabrication of high conductive electrodes(Springer New York LLC barbara.b.bertram@gsk.com, 2019) Manjunath, G.; Pujar, P.; Gupta, B.; Gupta, D.; Mandal, S.In this contribution, screen printing of aqueous based particle-free silver ink is addressed using combustion chemistry, where inks embody a redox mixture of silver nitrate and citric acid in the presence of a binder, sodium-carboxymethylcellulose. The exothermic reaction at ~ 176 °C results in the formation of pure silver. Screen-printing process is optimized for three different silver loadings (14%, 18% and 22%) in ink. In depth rheological study of the inks reveals thixotropic nature and the ink with 18% of silver possessing a viscosity of 328 Pa.s has a recovery rate of 84% at 110 s with a shear rate of 1 s?1. The deposited silver films (~ 3 µm thick) on both rigid-glass and flexible-polyamide substrates have shown an electrical conductivity of 4.2 × 106 S m?1 and 2.6 × 106 S m?1 respectively. Film adhesion on glass substrates categorized under 3B as per ASTM D-3359. Present screen-printed silver films find their application as a gate electrode in thin film transistors (TFTs). The TFTs comprising of indium zinc tin oxide–semiconductor and sodium ? -alumina dielectric with screen-printed silver as a gate electrode exhibited the saturation mobility, on:off ratio and threshold voltage of 0.88 cm2 V?1 s?1, 102 and ~ 0.3 V respectively. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.Item Combustion aided in situ consolidation of high strength porous ceramic structures with a minimum thermal budget(Elsevier B.V., 2020) Pujar, P.; Pal, A.; Mandal, S.The exothermic reaction between a pair of combustible pore formers (urea-ammonium nitrate) is the driving force in realizing low-temperature consolidation of hydroxyapatite (HA) particles. The particles are allowed to sinter in the proximity to the combustible pore formers. The exothermic (?H°rea = -898 kJ/mol) redox reaction between combustible pore formers is successfully utilized in deriving high compressive strength (~24 MPa) of HA at 300 °C. The evolution of gaseous products of combustion results in an interconnected porous network of HA. The estimated compressive strength of sintered HA at 300 °C is comparable with high temperature (1100 °C) conventionally sintered HA, at a fixed open porosity (~40%); which depicts nearly ~82% achievement with a reduction of sintering temperature by ~72%. Also, the pellets sintered at 600 °C have shown ~90% achievement in compressive strength of sintered HA. Further, the saturated pore area of 15% requires a sintering time of 9.58 h at a sintering temperature of 600 °C. Thus, combustion-assisted sintering is an alternative technique proves its potentiality in achieving remarkable compressive strength and paves the way for low-cost porous ceramics. © 2020 Elsevier B.V.