Effects of oxygen defects on structure and properties of Sm0.5Sr0.5CoO3-δ annealed in different atmospheres

Samples of Sm0.5Sr0.5CoO3–δ were annealed in different atmospheres（Ar,N2,and O2） and temperatures（400 1200 oC）,and changes in their masses,structures,surface transport properties,optical properties,and oxygen nonstoichiometries were investigated using thermogravimetric（TG） analyses,X-ray diffraction（XRD） analyses,electrical conductivity measurements,reflection spectra measurements,and X-ray photoelectron spectroscopy,respectively.The TG analyses,performed in air and an N2 atmosphere,allowed us to determine the changes in the masses of the samples.The results of the XRD analyses elucidated the changes in the structure of the samples under different conditions.The XPS spectra and simulation data indicated that the number of oxygen defects generated in the samples depended on the temperature and atmosphere.At high temperatures,the surface conductivities and full-spectrum reflectivities of the samples decreased with an increase in the number of oxygen vacancies.In an oxidative atmosphere,the samples exhibited outstanding visible and near-infrared light absorption.Furthermore,the samples were highly sensitive to a reducing atmosphere at various temperatures.On the basis of the fact that the properties of Sm0.5Sr0.5CoO3–δ vary with the environment,it has potential use in high-temperature applications such as weather sensors.     

钙钛矿氧化物Sm1-xSrxCoO3-δ的非化学计量氧含量测定方法比较

采用碘定量滴定和X射线能谱分析对钙钛矿氧化物Sm1-xSrxCoO3-δ(x=0.2,0.3,0.5,0.7,0.8)体系进行了非化学计量氧含量的测定。研究表明,两种测试结果变化趋势一致,各有优劣。采用直流四探针法研究了氧空位浓度与导电性能的关系,结果表明,随着Sr掺量的增加,Sm1-xSrxCoO3-δ氧空位浓度增加,在x=0.5时导电性最佳,原因是氧空位浓度过高会导致空位团簇,减少有效空位,影响电子-离子的传导。