Gas Sensing with Perovskite-like Oxides Having ABO3 and BO3 Structures

Abstract

WO 3 and LaFeO 3 are considered as example oxides in gas sensing, respectively of perovskitelike BO 3 and ABO 3 oxide groups, the structural chemistry of which is based on corner-sharing octahedral oxygen networks where transition metal cations B occupy the octahedral cages of oxygen anioins. WO 3 is an n-type semiconductor and many magnetic perovskites like LaFeO 3 are p-type semiconductors. There is a great flexibility inherent in the structure of both oxide groups which gives a lot of possibilities for structure engineering of the oxides for gas-sensing applications, e.g., by a temperature treatment or by modifying with impurity atoms. We have used here a high-temperature process, advanced reactive gas deposition, to produce nanoparticle thick films of WO 3 with the metastable tetragonal crystal structure at low temperatures up to 300-400 • C, and sol-gel citrate method to produce nanocrystalline LaFeO 3 powder as pure and modified with Sr and Mg, respectively.

Synthesis of three-dimensionally ordered macroporous LaFeO3 with enhanced methanol gas sensing properties

“…In fact, high temperature operations always lead to a decrease in the sensitivity to flammable gases. For this reason, researchers have investigated LaFeO 3 on its gas sensing properties [15][16][17][18][19].…”

Gas‐Sensing Properties of Perovskite BiFeO3 Nanoparticles

“…Taking the electron structure of the surface Fe ions (i.e., coordinately unsaturated d ‐orbitals because of the missing oxygen legends) 16 into consideration, one may expect a high gas sensitivity in BFO nanoparticles because the dangling bonds can provide geometrically and electronically favorable sites for molecule chemisorption, which is an important prerequisite for gas‐sensoring property. The small grain size can further enhance the performance by increasing the surface‐to‐volume ratio.…”

Gas Sensors for Monitoring Air Pollution

“…They are nonstochiometric compounds and p-type semiconductors whose conductivity is estimated through the holes created by the surplus oxygen therein. Substitution at the A-site of an element with a different valence (e.g., the replacement of La 3+ by Sr 2+ ) leads to the formation of oxygen vacancies and highvalence cations at the B-site, which results in a significant change in the catalytic activity [57][58][59][60]. When these sensing materials are exposed to reducing gases like CO, CH 4 , and HCHO, their conductivity decreases, and their resistance increases because of the chemical surface reactions between the reducing gas and the surplus oxygen [61][62][63].…”