Faculty Publications
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Item 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.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.