Rare earth oxycarbonates as a material class for chemoresistive CO 2 gas sensors (original) (raw)
Related papers
Rare-Earth Based Chemoresistive CO2 Sensors and Their Operando Investigations
Proceedings, 2019
Rare-earth oxycarbonates have been proposed as promising chemoresistive materials for CO2 sensors. In this contribution we present the results of a broad investigation focused on selecting the best candidates in the rare-earth compounds and, in the case of the best performing material, preliminary results dealing with the understanding of sensing by the operando methods.
A new CO< sub> 2 gas sensing material
Sensors and Actuators B: …, 2003
A new material for CO 2 sensing based on resistive changes is described. Using hydrated LaCl 3 as precursor and through two different synthesis routes-simple oxidation and a sol-gel-derived method-LaOCl powders are obtained. The main sensing characteristics of these powders are analysed, with special emphasis on (a) their response to CO 2 at a wide range of relative humidities and (b) their cross-sensitivity with CO. Compared with other metal oxide-based materials, lanthanum oxychloride offers a low working temperature and an improved sensor response in both dry and humid atmospheres.
Chemiresistive gas sensing properties of nanocrystalline Co3O4 thin films
Sensors and Actuators B: Chemical, 2013
The chemiresistive gas sensing characteristics of Co 3 O 4 thin films -prepared by electron-beam deposition of Co films on (0 0 0 1) Al 2 O 3 substrate followed by oxygen annealing at three different temperatures (500 • C, 650 • C and 800 • C) -have been investigated for a host of gases (C 2 H 5 OH, CO, NO, Cl 2 , NH 3 and H 2 S). The results of atomic force microscopy and X-ray diffraction revealed that the grains of these films are composed of nano-crystallites (size: 24-56 nm). X-ray photoelectron spectroscopy data revealed that the content of adsorbed oxygen decreases with increasing annealing temperature. For H 2 S gas in the concentration range 1-100 ppm, films annealed at 650 • C exhibited high selectivity, low base line drift and highest response, which are attributed to small crystallite size, improved crystallinity, better grain-to-grain connectivity and higher adsorbed oxygen content. The H 2 S sensing mechanism has been explained on the basis of the depletion of chemisorbed oxygen at the film surface.
A new CO2 solid state based gas sensor
2002
SUMMARY A new material for CO2 sensing is introduced. We describe the synthesis process and present the results of testing its main features as CO2 gas sensor comparing it with other materials. The crosssensitivity with CO and humidity is also analysed. Keywords: CO2 gas sensor, LaOCl
Structure-Dependent CO2 Gas Sensitivity of La2O2CO3 Thin Films
Journal of Sensors
Rare earth oxycarbonates are potential candidate materials for constructing simple and low-cost chemiresistive sensors for monitoring carbon dioxide (CO2) gas in the living and working environment for personal comfort and health reasons. Also, measurement of CO2 concentrations is needed in many industrial processes. Specifically, sol-gel made nanoparticles of Nd and La oxycarbonates have been studied previously as novel CO2 gas sensor materials. In this paper, pulsed laser deposition of La oxycarbonate (La2O2CO3) thin films was studied and structural properties of obtained thin films were characterized. Also, CO2 gas sensing ability of synthesized films was evaluated. The films deposited under CO2 partial pressure in various conditions were all Raman amorphous. In situ or ex situ annealing procedure at high CO2 partial pressure was needed for obtaining crystalline La2O2CO3 films, whereby hexagonal and monoclinic polymorphs were obtained in ex situ and in situ processes, respectively...
Sensors and Actuators B: Chemical, 2011
A series of nanostructred La 1−x Ce x CoO 3 perovskite-type (x ranging from 0 to 0.2), with a crystallite size of around 10 nm and a specific surface area of up to 55 m 2 /g were prepared using the activated reactive grinding method. XRD results showed that Ce segregates as CeO 2 when the addition level exceeds 10 at%. CO was chosen as a typical reducing gas and its interaction with surface oxygen was investigated. TPD-O 2 was used to investigate the effect of Ce-doping on total surface oxygen. The experimental results confirmed a positive effect of Ce-doping of up to 10 at% on total surface oxygen (␣-O 2). TPD-CO and XPS analyses were performed to find the total carbon adsorption (i.e. related to the adsorption of CO) on the surface of the synthesized samples. Both methods confirmed that more carbon adsorbs on the surface of doped formulations compared to the pure LaCoO 3. Ce-doping increases the surface oxygen, thereby facilitating the adsorption and oxidation processes. CO gas sensing properties of thick La 1−x Ce x CoO 3 films were performed. La 0.9 Ce 0.1 CoO 3 showed the highest conductivity and the lowest activation energy. The optimum CO sensing temperature for doped formulation was found to be 100 • C compared to 130 • C for pure perovskite. Ce-doped samples showed a maximum response ratio of 240% with respect to 100 ppm CO in air compared to 60% obtained with pure LaCoO 3 .
Metal-oxide semiconductors for carbon monoxide (CO) gas sensing: A review
Applied Materials Today, 2019
The development of metal-oxide semiconductor (MOS) based gas sensor has engrossed demanding research interest in the last several decades because of their potential for the selectivity, high sensitivity and fast detection of various toxic gases. Carbon monoxide (CO) is odorless, colorless and one of the most toxic gases. In this review recent progress on the development of different MOS based nanostructure for CO gas sensor is summarized. The commonly investigated classes of materials are MOSs (notably, zinc oxide and tin oxide) and yttrium stabilized zirconium. Recently, many metal oxide semiconductor including tin oxide, zinc oxide, titanium oxide, indium oxide, tungsten oxide, cerium oxide, copper oxide, composite MOS etc have been tested for CO gas sensing. The main focus is on new approaches for the synthesis of CO gas sensor by various researchers to improve the sensing performance like selectivity, sensitivity, response and recovery time with different materials and catalysts used.
Sensors and Actuators B: …, 2011
A series of nanostructred La 1−x Ce x CoO 3 perovskite-type (x ranging from 0 to 0.2), with a crystallite size of around 10 nm and a specific surface area of up to 55 m 2 /g were prepared using the activated reactive grinding method. XRD results showed that Ce segregates as CeO 2 when the addition level exceeds 10 at%. CO was chosen as a typical reducing gas and its interaction with surface oxygen was investigated. TPD-O 2 was used to investigate the effect of Ce-doping on total surface oxygen. The experimental results confirmed a positive effect of Ce-doping of up to 10 at% on total surface oxygen (␣-O 2). TPD-CO and XPS analyses were performed to find the total carbon adsorption (i.e. related to the adsorption of CO) on the surface of the synthesized samples. Both methods confirmed that more carbon adsorbs on the surface of doped formulations compared to the pure LaCoO 3. Ce-doping increases the surface oxygen, thereby facilitating the adsorption and oxidation processes. CO gas sensing properties of thick La 1−x Ce x CoO 3 films were performed. La 0.9 Ce 0.1 CoO 3 showed the highest conductivity and the lowest activation energy. The optimum CO sensing temperature for doped formulation was found to be 100 • C compared to 130 • C for pure perovskite. Ce-doped samples showed a maximum response ratio of 240% with respect to 100 ppm CO in air compared to 60% obtained with pure LaCoO 3 .
CO Sensing Properties of Nanostructured La0.8Sr0.2CoO3 Sensors Synthesized by EDTA-Glycol Method
Sensors & Transducers, 2008
We report a simple method for the preparation of pure LaCoO3 and La1-xSrxCoO3 (x = 0.1, 0.2 and 0.25) nanostructures by the EDTA-Glycol method. The final powders obtained by this method have been investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements. The gas sensitivity of pure and Sr doped LaCoO3 samples were investigated for CO, NH3, H2 and LPG. La0.8Sr0.2CoO3 powders (sample GIII) calcined at 6500C, exhibited a good sensor response towards CO gas at 2500C. On impregnation of 1 wt.% Pd over sample GIII, the operation temperature reduced to 2000C with a significant rise in sensitivity. The response time also decreases from about 3.5 min for sample GIII to less than 2.5 min for the Pd loaded element. The electronic interaction between Pd and metal oxide semiconductor is proposed to account for the sensitization effect.
Sensor Letters, 2012
Cobalt oxalate hydrate micro/nano structures have been successfully obtained using ultrasonic irradiation. The as-prepared Cobalt oxalate hydrate structures were calcinated at different temperatures to convert them into Co 3 O 4 rods. XRD, Thermo gravimetric analysis and FTIR spectroscopy were used to confirm the chemical composition and the phase purity. The scanning electron microscopy (SEM) reveals the formation of Co 3 O 4 microrod structure with aggregated nanoparticles which later get transformed in to nanospheres having a diameter of about ∼100 nm at a higher calcination temperatures. Thus two different nanostructures have been obtained and this provoked the interest to apply them to sensitivity measurements as they would differ in their surface areas, which forms the basic essentiality for semiconducting metal oxide gas sensors. BET analysis has been taken to study the surface area and its effect on sensitivity has been discussed for both the rods and nanospheres. The nanorods with larger surface area were found to exhibit the highest sensitivity towards acetone.