Papers by Narendra Pandey
Bulletin of Materials Science, 2012
This paper reports morphological and relative humidity sensing behaviour of ZnO-TiO 2 nanocomposi... more This paper reports morphological and relative humidity sensing behaviour of ZnO-TiO 2 nanocomposite powder pellets obtained through solid-state reaction route. Resistance of the pellets is observed to decrease with increase in relative humidity in the 10-90% range. Sensing element with 15 wt % of TiO 2 in ZnO shows best results with a sensitivity of 9•08 M /%RH in 10-90% relative humidity range. This sensing element manifests crystallite size of 71 nm as measured from XRD and average grain size of 207 nm calculated from SEM micrograph. This sensing element manifests low hysteresis, less effect of ageing and good reproducibility. Response and recovery times of this sensing element are measured to be 84 s and 396 s, respectively.
This review paper encompasses a study of metal-oxide and their composite based gas sensors used f... more This review paper encompasses a study of metal-oxide and their composite based gas sensors used for the detection of ammonia (NH3) gas. Metal-oxide has come into view as an encouraging choice in the gas sensor industry. This review paper focuses on the ammonia sensing principle of the metal oxides. It also includes various approaches adopted for increasing the gas sensitivity of metal-oxide sensors. Increasing the sensitivity of the ammonia gas sensor includes size effects and doping by metal or other metal oxides, which will change the microstructure and morphology of the metal oxides. Different parameters that affect the performances like sensitivity, stability and selectivity of gas sensors are discussed in this paper. Performances of the most operated metal oxides with strengths and limitations in ammonia gas sensing applications are reviewed. The challenges for the development of high sensitive and selective ammonia gas sensors are also discussed.
Physica B: Condensed Matter
International Journal of Materials Science and Applications
Paper reports humidity sensing studies of V 2 O 5-ZnO nanomaterial. When sample of V 2 O 5-ZnO an... more Paper reports humidity sensing studies of V 2 O 5-ZnO nanomaterial. When sample of V 2 O 5-ZnO annealed at 500°C was exposed to increasing humidity, resistance decreased. Aging over six months was within ±6% for ZnO and ±2% for V 2 O 5-ZnO; hysteresis was within ±6% for both ZnO and V 2 O 5-ZnO sensing elements. Grain size for pure ZnO was 620 nm, and 400 nm for V 2 O 5-ZnO nanomaterial. XRD suggested a distribution of crystallite size. For ZnO-V 2 O 5 , distribution in the crystallites size was as wide as 130% compared to only 20% for ZnO. Sensitivity of ZnO-V 2 O 5 nanomaterial was 500% more compared to ZnO sample.
International Journal of Scientific Research in Physics and Applied Sciences
MnO 2 doped nanostructured zinc oxide was synthesized by solid state reaction route. The prepared... more MnO 2 doped nanostructured zinc oxide was synthesized by solid state reaction route. The prepared material was characterized by X-ray diffraction, scanning electron microscope and UV-Vis absorption spectroscopy. The doping of MnO 2 in ZnÒ enhanced the crystallization and decreased the crystallite size. Surface morphology of the sensing material showed that the hexagonal shaped particles were uniformly distributed in zinc oxide that left large number of pores. These pores acted as humidity adsorption sites. With increase in the concentration of MnO 2 , the pores also increased. The optical band gap of pure ZnO was 4.05 eV. The value of band gap decreased with increase in the MnO 2 doping concentration. The average sensitivity of undoped zinc oxide was 3400 KΩ/%RH. The sensitivity of the sensing element increased with increase in the doping concentration. Sensitivity of MnO 2 doped ZnO composite is more than four times the sensitivity of pure zinc oxide at annealing temperature 600 o C.
Materials Today: Proceedings
International Journal of Applied Ceramic Technology, 2016
This paper reports the characterization and humidity sensing studies of CuO–ZnO nanocomposites pr... more This paper reports the characterization and humidity sensing studies of CuO–ZnO nanocomposites prepared by solid-state reaction method. The electrical resistance of nanocomposites continuously decreased when relative humidity (RH) was increased from 10% to 95% RH. Nanocomposites with 1 wt% of CuO in ZnO showed the best results with a sensitivity of 29.95 MΩ/%RH. This sample also showed low hysteresis and high reproducibility. This sample had an average particle and crystallite size of 200 nm and 70 nm, respectively. Measurement of crystallite size by both the methods, that is, Scherer's formula and Williamson and Hall method matched with an error of ±4%.
Sensors and Actuators A: Physical, 2016
Abstract Paper reports activation energy and humidity sensing studies of SnO 2 -doped ZnO nanomat... more Abstract Paper reports activation energy and humidity sensing studies of SnO 2 -doped ZnO nanomaterial prepared by solid-state reaction route. Prepared nanopowders were hydraulic-pressed to form pellets and annealed at temperatures of 400 °C to 700 °C. Pellet samples of SnO 2 -doped ZnO nanomaterials with 2, 6, 10, 15 and 16 wt% of SnO 2 in ZnO were prepared. XRD showed peaks of tetragonal cassiterite and hexagonal zincite. For the best sample of 15% SnO2-doped ZnO nanomaterials, the crystallite sizes were in the range of 27–124 nm evaluated from XRD. Average grain size for this sample as measured from SEM micrograph was 198 nm. SEM micrograph suggested agglomeration of smaller crystallites to form larger grains. Low activation energy value suggested that the sample could be used at room temperature. An increase of SnO 2 percentage in ZnO as well as the increase in annealing temperature both enhanced the sensitivity of the sample. Sensing element of 15 wt% SnO 2 -doped ZnO, annealed at 700 °C, showed the best results with sensitivity of 32.16 MΩ/%RH in the 15%–95% relative humidity range. Properties like low hysteresis, less effect of ageing and high reproducibility were exhibited by this sample.
IEEE Sensors Journal, 2015
This paper reports characterization and humidity sensing studies of pure zinc oxide (ZnO) andAl&l... more This paper reports characterization and humidity sensing studies of pure zinc oxide (ZnO) andAl<sub>2</sub>O<sub>3</sub>-doped ZnO nanomaterials prepared by solid-state reaction route. Pellet samples of ZnO-Al<sub>2</sub>O<sub>3</sub> nanocrystalline powders with 3, 5, 10, 15, and 20 wt% of Al<sub>2</sub>O<sub>3</sub> in ZnO were prepared. Pellet samples of pure ZnO were also prepared. Pellets were annealed at temperatures of 400 °C to 700 °C. Prepared powders were given pellet shape by applying pressure of 260 MPa. When samples were exposed to humidity it was found that as relative humidity (RH) increased, resistance of pellets decreased for the range of humidity from 10% to 90% RH range. Sample with 15 wt% of Al<sub>2</sub>O<sub>3</sub> in ZnO and annealed at 700 °C showed the best results with sensitivity of 14.98 MΩ/%RH. For this sensing element repeatability over different cyclic operations was within ±2% of the measured values of sensitivity after six months. Response and recovery time of sensing element of 15% Al<sub>2</sub>O<sub>3</sub> in ZnO were found to be 85 and 286 s, respectively. This sensing element manifested lower hysteresis, less effect of ageing and high reproducibility for annealing temperature 700 °C. X-ray diffraction pattern of this sensing element showed peaks of cubic gahnite and hexagonal corundum. Scherrer's formula gave crystallite size for the sensing elements of pure ZnO and Al<sub>2</sub>O<sub>3</sub>-doped ZnO in 18-96- and 23-98-nm range, respectively. Average grain size measured from scanning electron micrograph for pure ZnO was 107 nm and for Al<sub>2</sub>O<sub>3</sub>-doped ZnO (AZ-15) 114 nm suggesting agglomeration of the crystallites in the sensing element to form larger grains.
Advanced Materials Research, 2009
Paper reports morphological and humidity sensing studies of WO3 and WO3-ZnO nanocomposite pellets... more Paper reports morphological and humidity sensing studies of WO3 and WO3-ZnO nanocomposite pellets prepared in the weight % ratio of 10:1, 4:1 and 2:1 by solid-state reaction route. The pellets have been annealed at temperatures of 300-500°C. XRD pattern shows peaks of ZnWO4 formed due to solid state reaction between WO3 and ZnO. SEM micrographs show that the sensing elements manifest porous structure. Granulation and tendency to agglomerate seen in the SEM micrograph are due to the presence of zinc ions in ZnWO4. Nanoparticles are having their sizes in the range 37-182 nm. The average Kelvin radius at 20°C room temperature is 27 Ả. Humidity sensing application of the pellets has been studied in a humidity control cabinet. It is observed that as relative humidity increases, there is decrease in the resistance of pellets in the range 10-85% RH. Sensing element of WO3-ZnO in 2:1 weight % ratio shows best results in 10-85 % relative humidity range. The average sensitivity of this sample...
Advanced Materials Research, 2011
Paper reports morphological and relative humidity sensing studies of ZnO-TiO2nanocomposite powder... more Paper reports morphological and relative humidity sensing studies of ZnO-TiO2nanocomposite powder pellets obtained through solid-state reaction route. When exposed to humidity, resistance of pellets decreases with increase in relative humidity from 10-90%. Sensing element with 15 weight % of TiO2in ZnO shows best results with maximum sensitivity of 9.08 MΩ/%RH in 10-90% relative humidity range. This sensing element manifests smallest crystallite size of 71 nm as measured from XRD and lowest grain size of 207 nm calculated from SEM micrograph. This sensing element has the lowest value of activation energy, and hence higher electronic conduction.
16th International Workshop on Physics of Semiconductor Devices, 2012
Paper reports morphological and humidity sensing application of Cu2O doped ZnO composite prepared... more Paper reports morphological and humidity sensing application of Cu2O doped ZnO composite prepared by solid state reaction. Pellet samples of ZnO-Cu2O nanocrystalline powders with 5, 10, 15 and 20 weight % of Cu2O in ZnO have been prepared. These pellets have been annealed at temperatures 200-500°C. When samples have been exposed to humidity, it has been observed that as relative humidity increases, resistance of the pellet decreases for the entire range of humidity from 10% to 90%. The sample with 20% of Cu2O doped in ZnO shows best results with sensitivity of 4.23 M¿/%RH when annealed at 500°C. This sensing element manifests lower hysteresis, less effect of ageing and high reproducibility for annealing temperature 500°C. For this sensing element the two values of activation energy corresponding to two slopes in Arrhenius plot are 0.0274 eV for the temperature range 200-400°C and 0.0839 eV for the temperature range 400-500°C. XRD pattern shows peaks of hexagonal zincite and monoclin...
International Journal of Applied Ceramic Technology, 2013
ABSTRACT Pellet samples of 0–4% weight Ag‐loaded WO3 prepared through soft chemical route were si... more ABSTRACT Pellet samples of 0–4% weight Ag‐loaded WO3 prepared through soft chemical route were sintered at 700°C and exposed to humidity. Resistance of the pellets decreased with increase in relative humidity. Sensitivity increased with increase in the % loading of Ag. Four percent Ag‐loaded WO3 showed maximum sensitivity of 2.38 MΩ/% RH in 20–90% relative humidity range. This sensing element manifests highest crystallinity as well as maximum void concentration. Hysteresis and repeatability for this sensing element after 6 months are within ±2%. A polynomial fit of the humidification data revealed a strong correlation between resistance and relative humidity.
Advanced Materials …, 2009
NK Pandey 1 , A Tripathi 2 , K Tiwari 3 , A Roy 4 ... Sensors and Materials Research Laboratory, ... more NK Pandey 1 , A Tripathi 2 , K Tiwari 3 , A Roy 4 ... Sensors and Materials Research Laboratory, Department of Physics, ... University of Lucknow, Lucknow-226007, UP India [email protected], [email protected], [email protected], ...
Advanced Materials Research, 2011
Paper reports morphological and relative humidity sensing studies of ZnO-TiO2nanocomposite powder... more Paper reports morphological and relative humidity sensing studies of ZnO-TiO2nanocomposite powder pellets obtained through solid-state reaction route. When exposed to humidity, resistance of pellets decreases with increase in relative humidity from 10-90%. Sensing element with 15 weight % of TiO2in ZnO shows best results with maximum sensitivity of 9.08 MΩ/%RH in 10-90% relative humidity range. This sensing element manifests smallest crystallite size of 71 nm as measured from XRD and lowest grain size of 207 nm calculated from SEM micrograph. This sensing element has the lowest value of activation energy, and hence higher electronic conduction.
… Workshop on Physics …, 2012
… Journal of Applied …, 2011
Pellet samples of 0–4% weight Ag‐loaded WO3 prepared through soft chemical route were sintered at... more Pellet samples of 0–4% weight Ag‐loaded WO3 prepared through soft chemical route were sintered at 700°C and exposed to humidity. Resistance of the pellets decreased with increase in relative humidity. Sensitivity increased with increase in the % loading of Ag. Four percent Ag‐loaded WO3 showed maximum sensitivity of 2.38 MΩ/% RH in 20–90% relative humidity range. This sensing element manifests highest crystallinity as well as maximum void concentration. Hysteresis and repeatability for this sensing element after 6 months are within ±2%. A polynomial fit of the humidification data revealed a strong correlation between resistance and relative humidity.
Journal of Biomedical …, 2011
This work reports a simple, quick and economical method to prepare WO3 nanomaterials. Prepared tu... more This work reports a simple, quick and economical method to prepare WO3 nanomaterials. Prepared tungsten trioxide materials have been sintered at 700 degrees C for three hours. The material has been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). Crystallite size of the WO3 nanostructures obtained by Shearer's formula are between 12 and 72 nm and their grain size by SEM are from 20 to 105 nm. The humidity-sensitive electrical properties of the WO3 nanomaterial have been studied using d.c. measurements.
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Papers by Narendra Pandey