Faculty Publications
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Item Effect of O2, N2 and H2 on annealing of pad printed high conductive Ag-Cu nano-alloy electrodes(Institute of Physics Publishing helen.craven@iop.org, 2018) Manjunath, G.; Anusha, P.; Salian, A.; Gupta, B.; Mandal, S.In this study, annealing of pad printed Ag-Cu based conducting ink was studied in oxidizing, inert and reducing atmosphere to verify its oxidation dependent conductivity. Ag-Cu manually was formulated adopting polyol method; where silver nitrate and copper nitrate serve as initial metal precursors. Polyvinylpyrrolidone (PVP), ethylene glycol and sodium borohydride act as a stabilizer, solvent and reducing agent respectively. The nanoalloys were with an average particle size ?48 ±15 nm, capped with polyvinylpyrrolidone to avoid agglomeration and stable in non-polar solvents. Formation of nanoalloy, Ag 90 wt%-Cu 10 wt%, was verified through a peak shift in UV-visible spectroscopy, found at 470 nm along with Nelson-Relay curve fitting and x-ray photoelectron spectroscopy study. The calculated lattice parameter of nanoalloy ?4.034 Å, was in between pure silver and copper. The crystallite size was calculated using Debye-Scherrer, Williamson-Hall isotropic strain model and Halder-Wagner method. Electrode patterns were printed on a glass substrate by pad printing and were annealed under O2, N2 and H2 atmosphere to study the oxidation kinetics of copper. A maximum conductivity of -6.6 ×;105 S m-1 was observed in inert atmosphere annealing as the conductivity is solely depends on the oxidation of copper; appears with uttermost Cu0 and least Cu2+ in x-ray photoelectron spectroscopy. High conductive space required between manually and dispersion ink can have a potential application as an electrode in printed electronics. Further refinement of size of the nanopaticles by polyol method could help to obtain the effect of quantum confinement. © 2018 IOP Publishing Ltd.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 Effect of annealing-temperature-assisted phase evolution on conductivity of solution combustion processed calcium vanadium oxide films(Springer, 2018) Manjunath, G.; Vardhan, R.V.; Salian, A.; Jagannatha, R.; Kedia, M.; Mandal, S.In thiswork, the effect of annealing temperature on the conductivity of solution-combustion-synthesized calcium vanadium oxide (CVO) films was studied. Conductivity was tailored by the appearance of the phases like CaVO3, CaV2O5 and Ca2V2O7 as a function of annealing temperature; CaVO3 and CaV2O5 are responsible for high conductivity, whereas V5+ presence in Ca2V2O7 contributes towards dielectric nature. Evolution of phases of CVO was identified through X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. A detailed conductivity measurement as a function of annealing temperature helps us to identify the decreasing trend of conductivity with increasing temperature up to 400°C; beyond this it behaves like an insulator. There was a stable conductivity while aging the films in ambient for a few days. This study revealed safe application temperature domain of CVO, and a clear correlation of electrical conductivity with the in-depth structural-compositional-morphological study. © Indian Academy of Sciences.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 Effect of lanthanum on the phase evolution of perovskite barium stannate synthesized through polymerized complex method(Elsevier Ltd, 2019) Prajapati, M.J.; Vardhan, R.V.; Mandal, S.In this study, electrically conductive perovskite lanthanum-doped barium stannate, LaxBa1-x SnO3-? (x = 0, 0.05, 0.1 and 0.15) ceramics were synthesized through polymerized complex method. The evolution of BaSnO3 phase with temperature and effect of La doping was investigated. Doping of La increased the lattice parameter from 4.1165 to 4.1208 Å, up to solubility limit (x = 0.1); doping further, secondary phase La2Sn2O7 appeared. BaSnO3 phase crystallization initiated at ?528 °C from the reaction of BaCO3 and SnO2 and was retarded by La doping causing an increment in phase formation temperature from 528.4 to 531.1 °C. Fourier transform infrared spectroscopy evidence substantial increment in (SnO3)2- absorption band with temperature strengthening diffraction responses. An incremental response in the electrical conductivity was observed by La doping with a maximum value of ?25 S cm?1, attributed to the generation of charge carriers by substitution of Ba with La ion and oxygen vacancies. In parallel, generated charge carriers also contributed towards the ionic reduction of Sn4+ to Sn2+ aiding the lattice enhancement. La-doped BaSnO3 ceramics can have a potential application in optoelectronic, thermoelectric devices and humidity sensors. © 2019 Elsevier Ltd and Techna Group S.r.l.