A Structural Investigation of La2(GeO4)O and Alkaline-Earth-Doped La9.33(GeO4)6O2

Berastegui, P.; Hull, S.; Garci, Fatma; Grîns, Jêkabs

doi:10.1006/jssc.2002.9724

Cited by 95 publications

(89 citation statements)

References 22 publications

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“…Overall the results clearly show that, in any structural model of apatite-type systems, the effect of interstitial oxide-ions on the neighbouring atoms 8 needs to be considered. It therefore explains the difficulty in obtaining reliable structural refinements of these apatite systems, and also accounts for the high thermal displacement parameters of the oxide-ions associated with the tetrahedra observed in structural studies of other apatite-type oxide ion conductors [4,10,17,19,28]. …”

Section: Local Distortion Around the Y Dopant (Due To The Significantmentioning

confidence: 93%

Neutron diffraction structural study of the apatite-type oxide ion conductor, La8Y2Ge6O27: location of the interstitial oxide ion site

2009

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Apatite-type rare earth silicates/germanates have attracted considerable interest recently due to their high oxide ion conductivities. Despite evidence in support of a conduction mechanism involving interstitial oxide ions, the exact location of the interstitial oxide ion sites continues to attract controversy. In this paper we report a neutron diffraction structural study for the high oxygen excess compound, La 8 Y 2 Ge 6 O 27 . The structural model indicates that the oxide ions are located between the GeO 4 tetrahedra, leading to significant localised distortions. These results, coupled with recent modelling studies, hence, support the conclusion that oxide ion migration proceeds via these tetrahedra.3

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Section: Local Distortion Around the Y Dopant (Due To The Significantmentioning

confidence: 93%

Neutron diffraction structural study of the apatite-type oxide ion conductor, La8Y2Ge6O27: location of the interstitial oxide ion site

2009

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“…This is manifested in high Anisotropic Thermal Displacement Parameters (ADP's) for the channel O5 oxygen site, particularly for U 33 , which corresponds to displacement along the channel c-direction 17 . In our recent investigation of the La 10-y Si 6-x Ga x O 26+z system 18 we also found high ADP's for the tetrahedral SiO 4 oxygen positions, and evidence of localised distortions of the tetrahedra.…”

Section: -Structural Determinationmentioning

confidence: 99%

Structural studies of apatite-type oxide ion conductors doped with cobalt

et al. 2005

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All compositions were shown to possess the hexagonal apatite structure, and the results confirmed that cobalt can be doped onto both the La and Si sites within the structure depending on the starting composition. The Co doping is shown to cause considerable local distortions within the apatite structure. In the case of Si site doping two compositions showed anisotropic peak broadening, which has been attributed to incommensurate ordering of oxygen within the apatite channels.

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“…Research interest in this area has grown following the initial reports by Nakayama et al of high oxide conductivities (>10 -3 Scm -1 at 500°C) in rare earth silicates, Ln 10-x Si 6 O 26+y , with the apatite structure [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. The structure of these materials is shown in figure 1.…”

Section: Introductionmentioning

confidence: 99%

Neutron diffraction and atomistic simulation studies of Mg doped apatite-type oxide ion conductors

et al. 2007

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In this paper, detailed studies of the effect of Mg doping in the apatite-type oxide ion conductor La 9.33 Si 6 O 26 are reported. Mg is confirmed as an ambi-site dopant, capable of substituting for both La and Si, depending on the starting composition. A large enhancement in the conductivity is observed for Si site substitution, with a reduction for substitution on the La site. Neutron powder diffraction studies show that in agreement with cation size expectations, an enlargement of the unit cell is observed on Mg substitution for Si, with a corresponding increase in the size of the tetrahedral sites. For Mg substitution on the La site, a contraction of the unit cell is observed, and the neutron diffraction results indicate that there is preferential occupancy of Mg on the La2 (1/3, 2/3, ≈0.5) site. Atomistic simulation studies show significant local structural changes affecting the oxide ion channels in both cases. Mg doping on the Si site leads to a local expansion of the channels, while doping on the La site results in a large displacement of the silicate O4 site, such that it encroaches the oxide ion channels. The observed differences in conductivities are discussed with respect to these observations.

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A Structural Investigation of La2(GeO4)O and Alkaline-Earth-Doped La9.33(GeO4)6O2

Cited by 95 publications

References 22 publications

Neutron diffraction structural study of the apatite-type oxide ion conductor, La8Y2Ge6O27: location of the interstitial oxide ion site

Neutron diffraction structural study of the apatite-type oxide ion conductor, La8Y2Ge6O27: location of the interstitial oxide ion site

Structural studies of apatite-type oxide ion conductors doped with cobalt

Neutron diffraction and atomistic simulation studies of Mg doped apatite-type oxide ion conductors

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