TY - JOUR
T1 - Local defect structures and ion transport mechanisms in the oxygen-excess apatite La-9.67(SiO4)(6)O-2.5
AU - Jones, AS
AU - Slater, PR
AU - Islam, MS
AU - Slater, Peter
PY - 2008/8/1
Y1 - 2008/8/1
N2 - Apatite-type oxides of general formula La9.33+x(SiO4)(6)O-2 + (3x/2) have been attracting considerable interest recently because of their observed high oxide-ion conductivity and potential use in solid oxide fuel cells (SOFCs), oxygen sensors, and ceramic membranes. In this paper, computer modeling techniques are used to investigate, at the atomic level, the energetics of defect formation, oxide-ion migration, and cation migration in the oxygen-excess apatite silicate, La-9.67(SiO4)(6)O-2.5. Recent research has suggested that oxide-ion conduction in these apatite systems proceeds by an interstitial mechanism. Our results support this view and have revealed how the flexibility of the SiO4 substructure plays a crucial role in facilitating oxide-ion migration: the presence of interstitial oxide ions creates pseudo-"SiO5" units, which can effectively pass along the c direction by oxygen transfer. La vacancy migration is also examined and, as expected, found to have a high energy barrier.
AB - Apatite-type oxides of general formula La9.33+x(SiO4)(6)O-2 + (3x/2) have been attracting considerable interest recently because of their observed high oxide-ion conductivity and potential use in solid oxide fuel cells (SOFCs), oxygen sensors, and ceramic membranes. In this paper, computer modeling techniques are used to investigate, at the atomic level, the energetics of defect formation, oxide-ion migration, and cation migration in the oxygen-excess apatite silicate, La-9.67(SiO4)(6)O-2.5. Recent research has suggested that oxide-ion conduction in these apatite systems proceeds by an interstitial mechanism. Our results support this view and have revealed how the flexibility of the SiO4 substructure plays a crucial role in facilitating oxide-ion migration: the presence of interstitial oxide ions creates pseudo-"SiO5" units, which can effectively pass along the c direction by oxygen transfer. La vacancy migration is also examined and, as expected, found to have a high energy barrier.
U2 - 10.1021/cm801101j
DO - 10.1021/cm801101j
M3 - Article
SN - 1520-5002
VL - 20
SP - 5055
EP - 5060
JO - Chemistry of Materials
JF - Chemistry of Materials
IS - 15
ER -