Faculty Publications

Now showing 1 - 3 of 3

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.
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.
A scalable screen-printed high performance ZnO-UV and Gas Sensor: Effect of solution combustion
(Elsevier Ltd, 2020) Manjunath, G.; Pujari, S.; Patil, D.R.; Mandal, S.
In the present study, scalable screen-printed Zinc Oxide (ZnO) based sensor was demonstrated to sense ultra-violet irradiation and gases such as ammonia (NH3), ethanol (C2H5OH), liquefied petroleum gas (LPG), chlorine (Cl2) and hydrogen sulphide (H2S). A facile solution combustion synthesis (SCS) route was adopted to synthesize high purity, homogeneous, nanocrystalline and highly reactive ZnO with favourable morphologies, microstructural parameters for the sensing performance using low-cost and less-violent fuels such as urea, citric acid and glycine. Fuel impacts on uniform particle size distribution, bond length, grain size, lattice strain enhanced the gas sensing potential in the synthesized powders. Films were fabricated by depositing synthesized powders on the glass substrate via screen printing approach using Na-carboxy methyl cellulose as a binder, water as a solvent and annealed at 500 °C for 2 h in ambient. Non-stoichiometric, phase pure and adhered thick films with optical band gap (3.17-3.25 eV) imparted gas sensing properties because of recombination of an electron-hole pair and intrinsic defects. ZnO films obtained from glycine-fuel system exposed to 100 ppm of NH3, C2H5OH, Cl2 and 50 ppm of H2S, exhibited good gas sensitivity of ~8, 5, 3 and 10 at an operating temperature of 50, 100, 200 and 100 °C respectively with a faster response and recovery speed. But, high sensitivity ~6 to 100 ppm of LPG at 350 °C in ZnO films from citric acid fuel-system. ZnO films obtained from glycine fuel system showed a high response to UV irradiation for exposing time of 90s. Low cost, high-performance sensor can be fabricated for the dual applications - alarming to prolonged exposure to harmful UV radiation and detection of a series of toxic and damaging gases. © 2019 Elsevier Ltd

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