abstract
Oxygen ion conductors with most symmetrical structures such as fluorite- and perovskite-related phases, rely on the mobility of oxygen vacancies. High-performance electrolytes; namely with the apatite type structure, recently developed, show dominant interstitial transport. In order to assess basic composition-conductivity relationships in a fluorite-derived C-type cubic structure with high tolerance to different types of oxygen defects, a series of Y2O3 based materials were studied by impedance spectroscopy in air in the range 700-1000 degrees C. Yttria doped with CaO exhibits reasonably high ionic conduction via the vacancy mechanism. Samples doped with ZrO2 and HfO2 possess oxygen interstitials as dominant defects, but show poor ionic conductivity when compared to Ca-doped materials. These tendencies, known for other fluorite-related phases such as pyrochlores, are opposite to those observed for apatite- and K2NiF4 type structures. Comparison of ionic conductivity levels in various oxide materials suggests that fast interstitial migration may be expected for complex multicomponent materials where the ion transport occurs in lattice fragments with high bond ionicity. Furthermore, conduction-affecting stereological parameters, to a great extent, depend on the relaxation of covalent fragments.
keywords
ELECTRICAL-PROPERTIES; TRANSPORT-PROPERTIES; SOLID ELECTROLYTES; ELECTRONIC TRANSPORT; LANTHANUM GALLATE; GD; ND; FE; LA8SR2SI6O26; LA9.33SI6O26
subject category
Materials Science
authors
Traqueia, LSM; Marques, FMB; Kharton, VV
our authors
Fernando Manuel Bico Marques
Full professor