Low-temperature transport properties of isovalent-substituted La0.9Sr0.1YbO3-δ ceramic materials

Proton-conducting oxides based on lanthanum ytterbates (LaYbO3) have been proposed as promising electrolytes due to their high chemical stability in aggressive atmospheres. To improve the transport properties of LaYbO3, a strategy of oxygen deficiency creation by acceptor-type doping is usually employed. However, the acceptor-doping strategy has some limitations related to the low solubility limit of the introduced dopants. To further improve the ionic transport of already doped LaYbO3, two strategies-isovalent doping (chemical factor) and sintering temperature (technological factor)-are deliberately used in the present work. The La0.9Sr0.1Yb0.8R0.2O3-& delta; (R = In, Er, Y, Dy) were synthesized using the standard citrate-nitrate technology. X-ray diffraction analysis showed that all the samples are single-phase and have an orthorhombic structure with space group of Pna2(1). Increasing the sintering temperature from 1400 to 1500 & DEG;C almost doubles the average grain size of the samples; as a result, the ceramics sintered at 1500 & DEG;C have higher grain boundary and total conductivities than those of the ceramics sintered at 1400 & DEG;C. Among the La0.9Sr0.1Yb0.8R0.2O3-& delta; ceramics sintered at 1500 & DEG;C, the Dy-substituted material exhibits the highest grain boundary and total conductivities that confirms dopant type affects the electrolyte microstructure which, in turn, affects its electrochemical response. Therefore, the La0.9Sr0.1Yb0.8Dy0.2O3-& delta; composition can be considered the most conductive among the studied series.