Effect of CeO2 doping on the structure, electrical conductivity and ethanol gas sensing properties of nanocrystalline ZnO sensor. (original) (raw)
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Highly Sensing Properties Sensors Based on Ce-doped ZnO and SnO2 Nanoparticles to Ethanol Gas
Journal of Research in Nanotechnology, 2016
A comparative study on the sensing properties of nanoparticles ZnO+ x wt% CeO2 and SnO2+ x wt% CeO2 (x = 0, 2, 4 and 6) sensors sintered at 400 oC toward ethanol gas have been carried out. The crystal structure and the particle size of the prepared samples were investigated by using XRD, IR and TEM techniques. XRD and IR investigation confirmed that the prepared ZnO and SnO2 have good crystalline character with average crystallite size of 34.5 and 7.2 nm respectively. The TEM study showed that the particles of the pure ZnO sensor nearly show a hexagonal shape which enhanced by the addition of CeO2. While the particles of the SnO2 sensors displayed fine structures with spherical shape. The electrical conductivity behavior of both oxides samples was nearly similar and the electrical conductivity values of ZnO sensors are higher than that of SnO2 sensors at the same conditions. The obtained gas sensing results showed that the SnO2 based sensors have high sensitivity values toward ethanol gas with lower operating temperature than that of ZnO based sensors. On the other hand, ZnO based sensors have slightly rapid response time and short recovery time than that of SnO2 based sensors.
Gas sensing performance of hydrothermally grown CeO2-ZnO composites
2014
The sensors based on cerium oxide-zinc oxide (CeO 2 -ZnO) composites were fabricated by using thick-film screen printing of hydrothermally grown powders. The structural, morphological investigations were carried out by using XRD, FESEM and TEM and these studies revealed that the synthesized products were grown in high-density and possessed well-crystallinity. Furthermore, the gas responses were evaluated towards the ethanol, acetone, liquid petroleum gas (LPG) and ammonia gases. The 2 wt% CeO 2 -ZnO composite exhibited excellent response of 94% at 325 1C and better selectivity towards ethanol with low response and recovery time as compared to pure ZnO and can stand as reliable sensor element for ethanol sensor related applications.
Studies on alcohol sensing mechanism of ZnO based gas sensors
Sensors and Actuators B: Chemical, 2008
Nanosized ZnO powder was synthesized by using a chemical precipitation method, and loaded with different dopants through impregnation. The as-prepared ZnO powder was characterized by XRD and TEM. The characterization results show that the as-prepared sample is wurtzite polycrystalline ZnO, the mean grain size is 30-40 nm, and there are three types of adsorbed oxygen (O 2 − , O 2 2− , and O 2− ) on the surface of the sample. The as-prepared ZnO powder shows excellent gas responses to alcohol and acetaldehyde, but no response to ethene. The sensing mechanism of ZnO was further studied with the help of gas chromatography (GC) associated with a fixed-bed reactor. The studies show that acetaldehyde, carbon dioxide and water are the only oxidation products of C 2 H 5 OH over ZnO. The gas response to C 2 H 5 OH is strongly dependent on the conversion ratio of C 2 H 5 OH to acetaldehyde. In addition, among all the dopants tested, Ru is the optimal dopant which can increase the response to C 2 H 5 OH, but cannot increase the conversion ratio of C 2 H 5 OH to acetaldehyde. Thus we suggest that the gas sensing mechanism of ZnO to C 2 H 5 OH is the mode controlled by chemisorption of negatively charged oxygen, and the sensitizing role of Ru in the ZnO sensor belongs to the electronic sensitization mechanism.
Preparation of High-Performance Room Temperature ZnO Nanostructures Gas Sensor
Acta Physica Polonica A
Zinc oxide (ZnO) nanostructures were deposited on glass substrates by physical vapor deposition technique. To improve the crystallinity of ZnO, oxidation treatment was conducted at 400 • for 1 h in an atmospheric environment. The films characteristics of the films were examined by X-ray diffraction, ultraviolet-visible spectroscopy, atomic force microscopy, and scanning electron microscopy. The X-ray diffraction results illustrated that the deposited films have a polycrystalline hexagonal structure. The ultraviolet-visible spectrum showed that the transmittance of the ZnO film has an energy gap of about 3.225 eV. The atomic force microscopy images indicated that the films have good homogeneity, and the scanning electron microscopy images reveal that they consist of spherical nanosized grains with a granular surface. The ZnO films revealed good sensing performance to acetone and ethanol gases at an operating temperature of 25 • C with suitable recovery and response times. The sensitivity measured by homemade gas sensor system was approximately 21.
Nanoparticles tin oxide gas sensors having the chemical formula SnO2 + x wt% CeO2 (x = 0, 2, 4 and 6) have been synthesized by chemical precipitation method and sintered at 400, 600 and 800 oC. The composition and the morphology of the prepared samples are investigated and characterized by using XRD, IR, SEM and TEM techniques. XRD and IR results confirmed the formation of SnO2 tetragonal rutile and CeO2 cubic structures. The SEM and TEM investigations revealed that the average particle size of SnO2 increased with increasing the sintering temperature and decreased with CeO2 additions. The electrical conductivity was found to increase with sintering temperature and CeO2 additions. The obtained gas sensing properties data explained that the sensor having 2 wt % CeO2 and sintered at 400◦C has the highest sensitivity, rapid response time and short recovery time to ethanol gas among the prepared sensors. The influence of sintering temperature and CeO2 content on the structure, electrical conductivity and ethanol gas sensing of SnO2 sensors is discussed.
Nanocrystalline ZnO thin film for gas sensor application
Journal of Ovonic Research
Nano-crystalline (NC) materials exhibiting small particle size and large surface area may be applied for gas sensors, for which an excellent surface effect is required. Thin films of zinc oxide (ZnO) have been deposited onto glass substrates using a simple and inexpensive ultrasonically spray pyrolysis technique. Aqueous methanolic solution of zinc acetate was used as a spraying solution. The concentration of the solution was 0.1 M. The films prepared at different substrate temperature were uniform and well adherent to the substrates. X-ray diffraction (XRD) studies showed that all the films were polycrystalline in nanosize scale. The SEM photographs reveal the nano-size of the constituents. The electrical resistivity of the films was found to be dependent on the deposition temperature. The room temperature electrical resistivity was found to be varying in the range 10 -5 to 10 -6 Ω cm -2 . The sample resistance is measured with the presence of CH 4 in Ar carrier gas. The obtained responses of the samples were studied where our data were analyezed on the basis Yamoze SnO 2 sensor.
Effect of pH on the morphology and gas sensing properties of ZnO nanostructures
Sensors and Actuators B: Chemical, 2012
Morphology dependent gas sensing behaviour of zinc oxide has been reported in this paper. Nanostructures of zinc oxide have been synthesized by following a precipitation route at various pH values of the precursor solution. Structural and morphological analyses were carried out by using XRD and FESEM techniques. The XRD pattern confirmed wurtzite hexagonal structure of ZnO. The FESEM study revealed that ZnO synthesized at pH 8 developed nanorod like structure, rods got fused together when synthesized at pH 9 and 10, whereas synthesis at pH 11 resulted in transformation of rods into nanoparticles. The thick films of synthesized samples were deposited on alumina substrate and their sensing response to methanol, ethanol and propanol was investigated at different operating temperatures. It was observed that all the sensors exhibited optimum sensing response at 400 • C. It has also been observed that sample prepared at pH 11, constituting nanoparticles, exhibited high sensing response than an assembly of nanorods prepared at pH 8-10. Sensing response of all the samples tested was significantly higher towards propanol vapour than towards that of methanol and ethanol.
Synthesis, characterization and fabrication of gas sensor devices using ZnO and ZnO:In nanomaterials
Dopant elements solegel a b s t r a c t Undoped and In-doped ZnO including nanoparticles and nanorods were successfully synthesized via sol gel method. Effect of different doping ratios (1, 5 and 10%) of indium as a dopant element was optimized for the highest gas sensitivity. The morphological structures of prepared Undoped and doped ZnO were revealed using scanning electron microscope (SEM) and the aspect ratios of nanorods were calculated. X-ray diffraction (XRD) patterns reveal a highly crystallized wurtzite structure and used for identifying phase structure and chemical state of both ZnO and ZnO doped with In under different doping ratios. Energy dispersive X-ray (EDS) analysis was performed to be confirming the chemical composition of the In-doped ZnO nanopowders. The gas sensitivity for O 2 , CO 2 and H 2 gases were measured for the fabricated gas sensor devices as a function of temperature for In-doped ZnO nanopowders and compared with un-doped ZnO films.