Studies on electrical properties and CO-sensing characteristics of La0.9□0.1FeO3

doi:10.1016/S1002-0721(10)60463-2

Journal of Rare Earths

Volume 29, Issue 4, April 2011, Pages 374-377

https://doi.org/10.1016/S1002-0721(10)60463-2 Get rights and content

Abstract

Semiconducting sensors offer an inexpensive and simple method for monitoring gases. Sensors based on the ABO₃-type composite oxides materials have an advantage of high stability. The perovskite structures of these compounds are preserved, when an A-site deficiency of some perovskite structure compounds was formed. However, they exhibit particular physical properties. In this paper, La_0.9□_0.1FeO₃ powder with an orthorhombic perovskite phase was prepared by sol-gel method. The electrical properties and CO-sensing characteristics of the La_0.9□_0.1FeO₃ were also investigated. The results demonstrated that the La_0.9□_0.1FeO₃ was a p-type semiconductor material. Compared with LaFeO₃, the conductance of La_0.9□_0.1FeO₃ was better than that of LaFeO₃. The sensor based on La_0.9□_0.1FeO₃ showed excellent CO gas-sensing characteristics.

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Characteristics and sensing properties of CO gas sensors based on LaCo<inf>1 − x</inf>Fe<inf>x</inf>O<inf>3</inf> nanoparticles
2017, Solid State Ionics
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Therefore, LaFeO3 can also be a favorable material for CO sensing at low temperatures. In fact, LaFeO3 has been used to detect CO, for example, La0.9 − 0.1FeO3 ceramic powder showed response to 100 ppm CO at 100 °C [13]. Based on the above analyses, LaCo1 − xFexO3, a solid solution of LaCoO3 and LaFeO3, could be very promising for the CO sensing at low temperatures; there must be an optimal x value for obtaining the best CO sensing performance at low temperatures.
LaCo_1 − xFe_xO₃ (x ranging from 0 to 1) nanoparticles were prepared using the co-precipitation method, and the CO gas sensing properties of LaCo_1 − xFe_xO₃ nanoparticles were investigated. The LaCo_0.3Fe_0.7O₃ sensor shows the highest response at 250 °C (S = 40.9), and reliable dynamic response-and-recovery to different CO concentrations at a temperature as low as 50 °C. On the other hand, the LaCo_0.2Fe_0.8O₃ sensor exhibits the fastest response and recovery in the entire temperature region of 250 to 450 °C. The excellent CO sensing properties could be ascribed to the intense oxidation of CO by adsorbed O₂ on the LaCo_1 − xFe_xO₃ (x = 0.6, 0.7, 0.8) surface.
Sensing performances to low concentration acetone for palladium doped LaFeO<inf>3</inf> sensors
2016, Journal of Rare Earths
The PdCl₂ was mixed with nanocrystalline powders LaFeO₃ and subsequently followed by an annealing of 800 °C. PdO phase was formed and almost distributed uniformly on the surface of LaFeO₃ nano-particles. With an increase of PdO amounts in composite powders, sensing sensitivity R_g/R_a to low concentration acetone or ethanol for Pd doped LaFeO₃ sensors increased at first, underwent the maximum with 2 wt.% PdCl₂ dopant, and then doped again. Interestingly, appropriate Pd doping in LaFeO₃ changed the selectivity behavior of gas sensing. LaFeO₃ sensor showed good selectivity to ethanol, but 2 wt.% Pd doped LaFeO₃ sensor showed good selectivity to acetone. The sensitivity for LaFeO₃ at 200 °C was 1.32 to 1 ppm ethanol, and 1.19 to 1 ppm acetone. Whereas the sensitivity for 2 wt.% Pd doped LaFeO₃ at 200 °C was 1.53 to 1 ppm ethanol, and 1.9 to 1 ppm acetone. The 2 wt.% Pd doped LaFeO₃ sensor at 200 °C showed very short response time (4 s) and recovery time (2 s) to 1 ppm acetone gas, respectively. Such results showed that 2 wt.% Pd doped LaFeO₃ sensor is a new promising sensing candidate for detecting low concentration acetone.
Correlation of carbon monoxide sensing and catalytic activity of pure and cation doped lanthanum iron oxide nano-crystals
2015, Sensors and Actuators, B: Chemical
Citation Excerpt :
Various perovskite oxides exhibit good CO gas sensing characteristics and catalytic CO oxidation activity. Table 4 [21–28] compares the CO sensing and its catalytic oxidation characteristics of various perovskite oxides with the work presented in this manuscript. Unlike all the tabulated reports, for LaFeO3 and LaFe0.8Co0.2O3, we have reported both sensing and catalytic oxidation characteristics of CO oxidation in the present manuscript.
For nano-crystalline cobalt (Co) and cobalt/lead (Pb) co-doped lanthanum ferrite (LaFeO₃) ceramics, we have investigated the carbon monoxide (CO) sensing characteristics. The catalytic activities toward CO oxidation were investigated for LaFeO₃ and LaFe_0.8Co_0.2O₃ powders. At an operating temperature as low as 175 °C, Co doped LaFeO₃ sensors exhibit excellent low concentration (<100 ppm) CO gas sensing characteristics. Also, La_0.8Pb_0.2Fe_0.8Co_0.2O₃ (LPFC) ceramics selectively senses CO at 150 °C. For LaFe_0.8Co_0.2O₃, 0.056 mmol of CO conversion per gram of catalyst was measured at 200 °C. On the other hand, for LaFeO₃ ceramics, CO conversions per gram of catalyst were recorded to be 0.004 mmol. The superior low temperature CO sensing characteristics of nano-crystalline LaFe_0.8Co_0.2O₃ ceramics correlates well with its excellent catalytic activity toward CO oxidation. For perovskite LaFe_0.8Co_0.2O₃ sensors it was demonstrated that lower metal-oxygen binding energy, favorable d-orbital electron configuration of Co cation, and nature of surface composition are the three dominant factors control its superior catalytic activity and the CO sensing characteristics.
Low temperature butane sensing using catalytic nano-crystalline lanthanum ferrite sensing element
2014, Sensors and Actuators, B: Chemical
Highly sensitive, low temperature butane sensing characteristics are reported for nano-crystalline lanthanum iron oxide sensor. The improved butane sensing characteristics of these sensors are explained to be due to their efficient catalytic nature toward butane oxidation. Through infra-red spectroscopy in conjunction with X-ray photoelectron spectroscopy analysis we have demonstrated that the sensor catalytic activity is due to the presence of surface adsorbed oxygen species and hydroxyl ions. The desorbed water and oxygen molecules (originate from the surface adsorbed oxygen and hydroxyl group), initiate the catalytic oxidative dehydrogenation of butane at an operating temperature as low as 250 °C. We have also investigated the hydrogen, carbon monoxide and methane sensing performance of lanthanum ferrite sensors. The sensor found to be cross-sensitive to these gases. Thus, the selectivity coefficients for lanthanum ferrite butane sensors were estimated to be 1.67 and 4.67 for 50 ppm hydrogen and carbon monoxide sensing respectively. We have reported that first Fourier transform in conjunction with principal component analysis is fruitful to address the cross-sensitivity of nano-crystalline lanthanum ferrite sensor toward butane, hydrogen and carbon monoxide sensing.
Investigation on electrical transport, CO sensing characteristics and mechanism for nanocrystalline La<inf>1-x</inf>Ca<inf>x</inf>FeO<inf>3</inf> sensors
2014, Sensors and Actuators, B: Chemical
Citation Excerpt :
It has been further pointed that when exposed to 100 ppm CO, La0.9□0.1FeO3 (here □ represents La vacancy) nanocrystalline powders exhibits two response peaks in the response vs. temperature curve. One peak is at about 100 °C and another one is at about 260 °C [45]. The later peak in response may be connected with the effect of La vacancies.
The appropriate doping of Ca in nanocrystalline LaFeO₃ not only reduces the electrical resistance, but also enhances the sensing response. A minimum of resistance for nanocrystalline La_1−xCa_xFeO₃ (x = 0–0.35) occurs at about x = 0.3 with a value of Fe⁴⁺/Fe³⁺≈1. The electrical conduction of La_1−xCa_xFeO₃ (x = 0–0.35) can be well described by the mechanism of small polaron hopping. Results of X-ray photoelectron spectroscopy (XPS) show that the proportion of adsorbed oxygen O_ads enhances monotonously with Ca doping from x = 0–0.35. However, there exists an optimal Ca content (about x = 0.2) for obtaining highest response to 200 ppm CO among La_1−xCa_xFeO₃-based sensors (0≤x≤0.35). Such results indicate that some parts of adsorbed oxygen species do not effectively release their electrons to the surface of La_1−xCa_xFeO₃ at higher Ca dopants. The gas sensing response to CO for La_1−xCa_xFeO₃ sensors depends not only upon the amount of adsorbed oxygen on grain surfaces of sensors, but also upon the desorption capabilities of adsorbed oxygen species through reacting with CO.
Advancements in lanthanide-based perovskite oxide semiconductors for gas sensing applications: a focus on doping effects and development
2023, Analytical Methods

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: Foundation item: Project supported by Shandong Natural Science Foundation (ZR2010BL002), Foundation of Science and Technology of Shandong Education Department (2010J10LB04) and the Foundation of Science and Technology of University of Jinan (2010XKY1010)

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Studies on electrical properties and CO-sensing characteristics of La0.9□0.1FeO3

Abstract

J. Rare Earths

J. Rare Earths

Thin Solid Films

Thin Solid Films

Mater. Sci. Eng., A

Sens. Actuators, B, Chem.

Physica B

Sens. Actuators, B, Chem.

Mater. Lett.

Studies on electrical properties and CO-sensing characteristics of La_0.9□_0.1FeO₃