Fe- and Al-doped apatite-type lanthanum silicates: Structure and property characterization

For the first time the local structure of Al- and Fe-doped apatite-type lanthanum silicates (ATLS) of different stoichiometries was systematically studied by using IR spectroscopy. In addition to previous 29Si MAS NMR study, data obtained confirm the possibility of [SiO4] group interaction in ATLS, being favored by the presence of cation vacancies in the apatite. Transport properties of the systems were studied by impedance spectroscopy and oxygen isotope exchange technique. The latter indirectly shows that not only channel/interstitial oxygen atoms can be involved in the oxide-ion migration but also those of tetrahedrons.