Tin Oxide Thick Film Research Articles

Sensing performance of lead monoxide-doped tin oxide thick film gas sensor

Sensing performance of lead monoxide-doped tin oxide thick film gas sensor

Sensing mechanism of PbO doped tin oxide thick film for detection of LPG

The present work studied PbO doped tin oxide (SnO2) based thick films using screen printing technique. We fabricated undoped and PbO-doped SnO2 thick film on an alumina substrate to be used as a sensor. There are three samples are prepared in the laboratory as S1 (SnO2 thick film), S2 (1 wt% PbO at firing temperature 800 °C), and S3 (1 wt% PbO at firing temperature 900 °C). The microstructural properties are observed using XRD data. XRD measurement reveals that the crystallite size in nanometric rage and it is ∼31.51 nm, 27.09 nm and 22.90 nm for S1, S2, and S3 respectively. The sensing performances of fabricated thick films are investigated at an operating temperature of 200 °C upon exposure to LPG concentration in the range of 0–5000 ppm. It is found that the maximum response of LPG at an operating temperature of 200 °C (5000 ppm) is 26 % and 20 % for S3 and S2 respectively. The response of sensor S3 is ∼2 times more sensitive to S1 and ∼1.47 time sensitive to S2 for LPG. Therefore the fabricated PbO–SnO2 sensor may use for appropriate detection of LPG and also observed the experimental result of the sensor are in good agreement with the predicted theoretical model.

Effect on Neural Pattern Classifier for Intelligent Gas Sensor by Increasing Number of Hidden Layer

Abstract: Neural networks are used to solve complex problem viz., speech and image recognition, pattern recognition (Pattern classification), computer vision etc. Pattern classification by using Back Propagation algorithm for an intelligent gas sensor application is presented. The classifier is trained using published data of thick film tin oxide sensor array. Its superior classification and learning performance is demonstrated for discrimination of alcohols and alcoholic beverages by increasing number of hidden layer. The new model proposed in this article give steep and monotone learning curve and better classification efficiency. Keywords: Neural Network classifier, Back Propagation Algorithm, system error, classification efficiency, learning curve

Theoretical modeling of Pd-SnO2 based ethanol gas sensor

In this paper, we fabricate two devices, undoped tin oxide (UTO) and 1 wt% palladium-doped tin oxide (PdTO) thick films for ethanol (C2H5OH) gas sensors. UTO and PdTO samples were deposited on alumina substrate using screen-printing technology. The fabricated UTO and PdTO sample was used as ethanol gas sensor in range (0-5000 ppm) at operating temperature 473 K. The results showed the highest response (∼71%) for varying concentrations of ethanol (5000 ppm) at operating temperature 473 K. Also response/recovery time was observed and it was ∼41 s / 125 s. our experimental data was well supported by the proposed theoretical model.

Developments of MEMS Gas Sensors Based on Tin Oxide semiconductors: Application to Battery-Powered Household Gas Alarms

Developments of MEMS Gas Sensors Based on Tin Oxide semiconductors: Application to Battery-Powered Household Gas Alarms

A new type low-cost, flexible and wearable tertiary nanocomposite sensor for room temperature hydrogen gas sensing

This paper reports on reduced graphene oxide (rGO), tin oxide (SnO2) and polyvinylidene fluoride (PVDF) tertiary nanocomposite thick film based flexible gas sensor. The nanocomposite of 0.90(PVDF) − 0.10[x(SnO2) − (1 − x)rGO] with different weight percentages (x = 0, 0.15, 0.30, 0.45, 0.6, 0.75, 0.90 and 1) have been prepared by the hot press method. Chromium (Cr) has been deposited on the surface by using E-beam evaporation system, which is used as electrode of the device. Crystal structure, morphology, and electrical characteristics of the device have been explored for the technological application. A correlation between crystallinity, morphology, and electrical properties with these thick films has also been established. The device has been tested at different hydrogen (H2) gas concentration as well as at different response times. A superior response of 0.90(PVDF) − 0.10[0.75(SnO2) − 0.25 rGO] nanocomposite thick film has been observed. Hence, this composition is considered as optimized tertiary nanocomposite for the hydrogen gas sensor application. The sensor response of 49.2 and 71.4% with response time 34 sec and 52 sec for 100 PPM and 1000 PPM H2 gas concentration respectively have been obtained. First time a new kind of low cost and flexible polymer based nanocomposite thick film gas sensor has been explored.

Apparatus for Seebeck Coefficient Measurements on High-Resistance Bulk and Thin-film Samples

The main challenge in thermoelectric metrology is an accurate Seebeck coefficient measurement on high electrical resistance bulk and thin-film samples, as the loading by the measuring device causes a considerable voltage drop on the internal resistance of the sample. It has been shown that this technical problem can be solved by utilizing the zero current technique of measurement. Here, an apparatus for the simultaneous measurement of the Seebeck coefficient and electrical resistance of bulk and thin-film samples using zero current measurement technique is presented, which automatically measures these quantities at different temperature profiles at steady-state, quasi-steady-state, and transient conditions in different atmospheres. Thick-film tin oxide microheaters are utilized to provide the desired temperature gradient along with the sample from room temperature up to 1200 K, and zero current method is used to eliminate errors originating from the high internal resistance of the sample. As examples, Seebeck voltages and electrical resistances are measured on the bulk and thin-film zinc oxide samples with internal resistances in the megohm ($\text{M}\Omega$ ) range. Operating the device for measurements involving time-varying temperature gradients is demonstrated.

Structural, Optical and Ethanol Sensing Properties of Dy-Doped SnO2 Nanoparticles

We report a facile co-precipitation synthesis of dysprosium (Dy3+) doped tin oxide (SnO2) thick films and their use as gas sensors. The doping percentage (Dy3+) was varied from 1 mol.% to 4 mol.% with the step of 1 mol.%. As-produced material with varying doping levels were sintered in air; and by using a screen printing technique, their thick films were developed. Prior to sensing performance investigations, the films were examined for structural, morphological and compositional properties using x-ray diffraction, a field emission scanning electron microscope, a transmission electron microscope, selected area electron diffraction, energy dispersive analysis by x-rays, Fourier transform infrared spectroscopy and Raman spectroscopic techniques. The structural analyses revealed formation of single phase nanocrystalline material with tetragonal rutile structure of SnO2. The morphological analyses confirmed the nanocrystalline porous morphology of as-developed material. Elemental analysis defined the composition of material in accordance with the doping concentration. The produced sensor material exhibited good response towards different reducing gases (acetone, ethanol, LPG, and ammonia) at different operating temperatures. The present study confirms that the Dy3+ doping in SnO2 enhances the response towards ethanol with reduction in operating temperature. Particularly, 3 mol.% Dy3+ doped sensor exhibited the highest response (∼ 92%) at an operating temperature of 300°C with better selectivity, fast response (∼ 13 s) and recovery (∼ 22 s) towards ethanol. The concise representation of conducted work: (a) EDAX, (b) ethanol sensing mechanism, (c) sensor response, and (d) SEM image of Dy: SnO2 nanoparticles.

Nanostructured SnO2 thick films for gas sensor application: analysis of structural and electronic properties

This research is focused on structural and electrical characterisation of tin oxide (SnO2) applied as a thick film and investigation of its properties as gas sensitive material. Micron sized SnO2 powder was milled in an agate mill for six hours to fabricate SnO2 nanopowder, which was afterwards sieved by 325 mesh sieve and characterized by XRD and SEM. This powder was used as functional part in the production of thick film tin oxide paste containing a resin vehicle with 4 wt. % nanosize glass frits acting as permanent binder. The glass frits where additionally milled for twelve hours in the agate mills to nanosized powder and sieved by a 325 mesh sieve as well. The achieved thick film paste was screen printed on alumina and fired at 850oC peak temperature for 10 minutes in air. After the sintering process, thick film samples where characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The reflectivity was measured on the same samples by UV-VIS spectrophotometer: the band gap was determined from the slope of reflectance. After that a matrix of different interdigitated electrode structure of PdAg paste was printed and sintered using the mentioned sintering conditions. The tin oxide thick film was printed over the interdigitated electrodes as a top layer and sintered again under the same conditions. The total electrical resistance was measured as a function of the electrode spacing and temperature. A negative temperature coefficient (NTC) was identified and measured in the range from room temperature (27°C) to 180°C in a climate chamber. Finally the samples were placed into a gas reactor with NOx and CO gas and the resistance was measured in the same temperature range (27°C-200°C).

Synthesis, characterization and LPG response of Pd loaded Fe doped tin oxide thick films

The nanocrystalline powders of undoped, Fe doped tin oxide and Pd (1, 2 and 3mol%) loaded Fe: SnO2 were synthesized by co-precipitation method and characterized by using TGA–DTA, XRD, FE-SEM, EDAX, TEM, SAED, FTIR and Raman spectroscopy techniques. Gas sensing properties were investigated towards various reducing gases viz. liquid petroleum gas (LPG), ethanol, ammonia and acetone vapor. All the SnO2 compositions revealed single phase solid solution formation. The TEM and SAED results of samples sintered at 650°C for 2h show particle size of 19nm for undoped SnO2 which was reduced to 5nm on loading of Pd in Fe: SnO2. It is found that loading of Pd in Fe doped SnO2 reduces the particle size and improves the gas response. The gas sensing measurements showed that the 3mol% Pd loaded Fe: SnO2 thick film sensor exhibited high response and good selectivity towards LPG at moderate operating temperature of 225°C.

Tin oxide thick film by doping rare earth for detecting traces of CO2: Operating in oxygen-free atmosphere

SnO2 thick films doped with atomic ratios ranging from 0 up to 8at.% La, 8at.% Gd, 8at.% Lu were fabricated, respectively, via hydrothermal and impregnation methods. The crystal phase, morphology, and chemical composition of the SnO2-based nanoparticles were characterized by XRD, FE-SEM, EDX, HRTEM and XPS. Sensing properties of La-SnO2, Gd-SnO2, Lu-SnO2 films, as well as the pure SnO2 film, were analyzed toward CO2 in the absence of O2. It was found that the optimal doping element was La and the best doping ratio was 4at.%. The maximum response appeared at an operating temperature of 250°C, on which condition the 4at.% La-SnO2 exhibited a remarkable improvement of response from 5.12 to 29.8 when increasing CO2 concentration from 50 to 500ppm. Furthermore, the working mechanism underlying such enhancement in CO2-sensing functions by La additive in the absence of O2 was proposed and discussed.

Effect of Temperature on Palladium-Doped Tin Oxide (SnO<SUB>2</SUB>) Thick Film Gas Sensor

Effect of Temperature on Palladium-Doped Tin Oxide (SnO<SUB>2</SUB>) Thick Film Gas Sensor

Low power consumption micro C2H5OH gas sensor based on micro-heater and screen printing technique

Micro C2H5OH gas sensor based on micro-heater and tin oxide thick film was fabricated by using complementary metal-oxide semiconductor (CMOS) compatible micro electro mechanical systems (MEMS) process, which showed low power consumption and high response. Semiconducting SnO2 nano-powders were synthesized via co-precipitation method, and to increase the sensitivity for alcohol gas rare metal dopants were added. Bridge type micro-heater based on Si substrate was fabricated by surface micromachining technique and in the structure of micro-heater, the resistances of two semi-circled Pt heaters are connected to the spreader for thermal uniformity. The response of the micro gas sensor was 0.78 for 2ppm alcohol with lower power consumption (35mW) than that of the commercial alcohol gas sensor. The mechanical stability of the sensor was tested under the higher direct current (DC) power than that of the normal operation power and the variation rate of the micro-heater resistance was below 2% after 105 times repetitive 35mW pulse operations.

Solid-state reaction synthesized Pd-doped tin oxide thick film sensor for detection of H2, CO, LPG and CH4

This paper deals with the synthesis of tin oxide (SnO2) nano-powders by a solid-state reaction technique. The synthesized powders have been characterized by simultaneous thermo gravimetric and differential thermal analysis (TG–DTA) and X-ray diffraction (XRD) techniques. Suitable calcination temperature is established by XRD and TG–DTA analysis. Thick film sensors have been developed from as-prepared undoped and palladium (Pd) doped (0.5 and 1 wt%) SnO2 powders using screen printing technology for the detection of various pollutant gases such as, hydrogen (H2), carbon monoxide (CO), liquefied petroleum gas (LPG) and methane (CH4). The surface of the thick film sensor has been characterized by field emission scanning electron microscopy (FESEM). The sensing characteristics of thick films have been studied from the aspect of crystallite size of sensing material and microstructure of the thick film surface. It is found that SnO2 doped with 1 % Pd exhibits the maximum sensitivity (79 %) towards CO gas along with fast response/recovery time (80 s, 197 s) and almost insensitive for H2, LPG and CH4.

Low-Power-Consumption Metal Oxide NO2 Gas Sensor Based on Micro-Heater and Screen Printing Technology

An NO2 micro gas sensor was fabricated based on a micro-heater using tin oxide nano-powders for effective gas detection and monitoring system with low power consumption and high sensitivity. The processes of the fabrication were acceptable to the conventional CMOS processes for mass-production. Semiconducting SnO2 nano-powders were synthesized via the co-precipitation method; and to increase the sensitivity of the NO2 gas rare metal dopants were added. In the structure of the micro-heater, the resistances of two semi-circular Pt heaters were connected to the spreader for thermal uniformity. The resistance of each heater becomes an electrically equal Wheatstone-bridge, which was divided in half by the heat spreading structure. Based on the aforementioned design, a low-power-consumption micro-heater was fabricated using the CMOS-compatible MEMS processes. A bridge-type micro-heater based on the Si substrate was fabricated via surface micro-machining. The NO2 sensing properties of a screen-printed tin oxide thick film device were measured The micro gas sensors showed substantial sensitivity down to 0.5 ppm NO2 at a low power consumption (34.2 mW).

Synthesis of Tin Oxide Thick Film and Its Investigation as a LPG Sensor at Room Temperature

Present paper reports the synthesis of SnO2, its characterization and performance as Liquefied Petroleum Gas (LPG) Sensor. XRD pattern revealed the tetragonal crystalline nature of the material. Crystallites sizes were in the range 14 - 30 nm. Tin oxide thick film was prepared by using screen printing technique. After that these were investigated through SEM. SEM image of thick-film surface was spherical in shape and porous. Further at room temperature, the film was exposed to LPG in a controlled gas chamber and variations in resistance with the concentrations of LPG were observed. The maximum value of average sensitivity of thick film was 37 MΩ/min for 5 vol. % of LPG. Sensor responses as a function of exposure and response times were also estimated and maximum sensor response were found 273 and 312 for 4 and 5 vol. % of LPG respectively.

High-response and low-power-consumption CO micro gas sensor based on nano-powders and a micro-heater

In this research, a CO micro gas sensor was fabricated based on a micro-heater by using a tin oxide nano-powder for effective gas detection and a monitoring system with low power consumption and high sensitivity. Tin-oxide-based nano-powders were fabricated using a conventional method and their structural properties were examined by using the scanning electron microscope, X-ray diffractor, etc. Membrane type micro-heater based on Si substrate was fabricated by using complementary metal-oxide semiconductor (CMOS) compatible micro electro mechanical systems (MEMS) process by using bulk micromachining. The gas sensing properties for slurry-dropped tin oxide thick film device were measured for CO gas. The micro gas sensors showed high sensitivity and low power consumption, about 15 mW power consumption, 2 ppm CO could be detected.

Fuzzy Entropy Based Neuro-Wavelet Identifier-Cum-Quantifier for Discrimination of Gases/Odors

In this paper, a new approach to design of an odor/gas identifier-cum-quantifier is presented. Dynamic response curves of an oxygen-plasma treated thick-film tin oxide sensor array exposed to four different gases were subjected to continuous wavelet transform (CWT). Appropriate wavelet coefficients were selected using multiscale principal component analysis (MSPCA). Fuzzy entropy and fuzzy subsethood values were calculated for the individual odor/gas and for the particular concentration band of each odor/gas, respectively. The quantitative information was encoded in the fuzzy subsethood values of the particular concentration bands in the output feature space, whereas the fuzzy entropy values were used to normalize the training data set consisting of MSPCA selected wavelet coefficients. A feedforward neural network was trained with a backpropagation algorithm with the training data containing the wavelet coefficients normalized with fuzzy entropies of individual odors/gases. The target data set was made up of the fuzzy subsethood values of the particular concentration band. The proposed network achieved identification and quantification of odors/gases with a 100% success rate. Also, fuzzy entropy based normalization helped to achieve 100% identification/quantification with a reduced number of sensors in the array.

Carbon dioxide sensitivity of La-doped thick film tin oxide gas sensor

The CO 2 sensitivity of a La-doped SnO 2 thick film was characterized with variation of the La 2O 3 content up to 4.5 mol%. Effects of mechanical milling of SnO 2 powders on the CO 2 sensitivity of a SnO 2 thick film sensor were also studied. When exposed to 1000 ppm of CO 2, the sensitivity of a SnO 2 thick film sensor was improved from 1.14 to 1.52 with increasing the La 2O 3 doping concentration from 0 mol% to 2.2 mol%. Enhanced sensitivities of 1.45–1.51 were obtained for the thick film sensors processed with mechanically milled SnO 2 powders.

Effect of the Particle Size of SnO_2:Ni on Gas Sensing Properties

Ni 8 wt.%-doped tin oxide () thick films were fabricated into gas sensors by the method of screen printing onto alumina substrates. The particle size of was controlled by changing the ball-mill time between 0~120 h. The structural and morphological properties of these thick films were investigated using X-ray diffraction and scanning electron microscopy. The structural properties of powders showed a tetragonal phase with (110) dominant orientation. The particle size of the :Ni powders after ball-mill of 120 h was about 0.05 . The gas sensitivity (S