Facile Synthesis, Microstructure, and Gas Sensing Properties of NdCoO₃ Nanoparticles

Abstract

NdCoO 3 nanoparticles were successfully synthesized by a simple, inexpensive, and reproducible solution method for gas sensing applications. Cobalt nitrate, neodymium nitrate, and ethylenediamine were used as precursors and distilled water as solvent. The solvent was evaporated later by means of noncontinuous microwave radiation at 290 W. The obtained precursor powders were calcined at 200, 500, 600, and 700 ∘ C in a standard atmosphere. The oxide crystallized in an orthorhombic crystal system with space group Pnma (62) and cell parameters = 5.33Å, = 7.52Å, and = 5.34Å. The nanoparticles showed a diffusional growth to form a network-like structure and porous adsorption configuration. Pellets prepared from NdCoO 3 were tested as gas sensors in atmospheres of carbon monoxide and propane at different temperatures. The oxide nanoparticles were clearly sensitive to changes in gas concentrations (0-300 ppm). The sensitivity increased with increasing concentration of the gases and operating temperatures (25, 100, 200, and 300 ∘ C).

Sensitivity Tests of Pellets Made from Manganese Antimonate Nanoparticles in Carbon Monoxide and Propane Atmospheres

“…This type of microstructure is attributed to the agglomeration of particles that grew due to the temperature and the chelating agent (ethylenediamine) employed during the synthesis process [5,7]. The porosity on the material’s surface was due to the release of gases produced during the thermal treatment of the material [26], which caused the decomposition of organic species but mainly water vapor, NO x and CO 2 [27]. …”

“…The surface area of the MnSb 2 O 6 powders, according to the BET (Brunauer–Emmett–Teller) method, was estimated at 14.6 m 2 /g. In general, mixed oxides usually have relatively low surface areas (<10 m 2 /g) when prepared by traditional methods [27]. The synthesis of sensor materials with larger surface areas can therefore favor the adsorption of gases and, consequently, increase their response.…”

“…The increase in the response of the MnSb 2 O 6 nanoparticles is mainly associated with the increase in the number of propane molecules that react with oxygen chemisorbed on the material’s surface due to the temperature [9,26,27]. Different authors have reported that variations in electrical resistance occur due to the increase in temperature, causing the sensitivity magnitude to increase [5,6,8,26,35,37].…”

“…The mechanism that accounts for the interaction between the propane molecules with the surface of the MnSb 2 O 6 pellets has not been fully explained [27]. However, it has been reported that some of the factors that affect the chemisorption of oxygen are the particle size and the morphology since if the size is less than twice the thickness of the charged outer layer $\left(L_S\right)$, the oxygen species that are adsorbed are $O^{-}$, which leads to an increased response [40,41].…”

Synthesis of ZnMn2O4 Nanoparticles by a Microwave-Assisted Colloidal Method and their Evaluation as a Gas Sensor of Propane and Carbon Monoxide

“…The mechanism that involves detection in propane atmospheres has not been fully studied. However, it has been suggested in the literature that C 3 H 8 molecules react with chemisorbed O − species, producing CO 2 , water vapor, and an electron release to the material’s surface [64], causing the changes in the material’s electrical resistance shown in Figure 8a,b. Other authors have studied the chemical interaction between the surface of a material and the molecules of the C 3 H 8 , suggesting some chemical processes that involve the adsorption–desorption of propane, and obtaining results such as those presented in this work [11,65,66].…”