Preparation And Gas Sensing Properties Of Chromium Oxide Based Microspheres

Pure chromium oxide porous microspheres with different diameters have been synthesized by ethanol solvothermal process without any template addition.The pure porous Cr2O3 material is three-dimensional spherical clusters consisting of primary nanoparticles.The ZnO-Cr2O3 porous microspheres and V2O5-Cr2O3 nanocomposites have been synthesized by the same reaction process.These materials were characterized by TG-DRA,IR,XRD,EDS,XPS,SEM and TEM techniques.Thick film-type sensors for all the materials were fabricated and their gas sensing properties to toluene,benzene,chlorobenzene,ethanol,and triethylamine were measured.The pure porous spherical Cr2O3 thick film sensor exhibites excellent gas sensing properties to aromatic molecules for the first time,especially showing better selectivity to toluene at 170 ?.The sensitivity of the sensor to 100 ppm toluene at 170 ? is 33.64 and the detection limit of toluene is 1 ppm.The sensor shows good response to ethanol at the same conditions(100ppm,S=36.1)and can detect as low as 0.5 ppm ethanol.The selectivity of the sensor to toluene can be greatly improved by addition of the zinc oxide in the Cr2O3 microspheres.The highest sensitivity of the ZnO-Cr2O3 microspheres to 100 ppm toluene can be obtained by addition of 10%zinc oxide(S=50.79)at 170 ?.For the case of the addition of V2O5,the conductivity type can be changed from the p-type conduction of pure Cr2O3 to the n-type one of V2O5-Cr2O3 nanocomposites.The V2O5-Cr2O3 nanocomposites exhibit response to triethylamine and the maximum response of the senor to 1000ppm triethylamine is 2.90 at 290 ?.The response/recovery time for the sensors can be obviously shortered by the addition of V2O5.