Oxide ionic conductivity of apatite type Nd9·33(SiO4)6O2 single crystal

Nakayama, Susumu; Sakamoto, Masatomi; Higuchi, Mikio; Kodaira, Kohei; Sato, Mineo; Kakita, Shinichi; Suzuki, Tetsuhito; Itoh, Katsuhiko

doi:10.1016/s0955-2219(98)00215-5

Cited by 172 publications

(103 citation statements)

References 7 publications

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“…Apatite-type Ln silicates, Ln9.33+2x/3(SiO4)6O2+x, (Ln: rare earth elements) and related materials are promising oxide-ion conductors and are used as electrolytes in high-temperature solid oxide fuel cells because of their high conductivity, which is comparable or superior to that of yttria-doped zirconia [1][2][3][4][5][6][7]. The high conductivity was first observed by one of the authors [1,2].…”

Section: Introductionmentioning

confidence: 99%

“…In the study of single crystal Nd-Si-O apatite, the conductivity along the c-axis was found to be greater than that perpendicular to the c-axis; however, the difference between them decreases with increasing temperature, suggesting that the oxide ions migrate along the 001 direction. Furthermore, the migration perpendicular to the c-axis becomes significant at elevated temperatures [3,5]. The maximum entropy method (MEM) has been used to fit the neutron diffraction patterns and to investigate the conduction mechanism.…”

Section: Introductionmentioning

confidence: 99%

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Oxygen-17 nuclear magnetic resonance measurements on apatite-type lanthanum silicate (La9.33(SiO4)6O2)

et al. 2012

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We used magic angle spinning (MAS), multiquantum (MQ)-MAS, and high-temperature (HT) nuclear magnetic resonance (NMR) measurements to investigate the oxide-ion conduction path of oxygen-17 (O-17) in apatite-type lanthanum silicate La9.33(SiO4)6O2. A highly crystalline apatite-type lanthanum silicate was specifically synthesized for the measurements. MAS and MQ-MAS NMR confirmed that four kinds of oxide-ion sites are present in the structure and showed a small extra peak (<1%) possibly due to an interstitial site. The high-temperature measurements showed that the line shape changed and sharpened with increasing temperature from 200 ˚C, and the peak position shifted at 700 ˚C. The comparison of the results between MAS NMR (room-temperature) and HT static NMR showed the exchange of oxide ions bonded to Si (O1, O2, and O3) but the apparent exchange between the oxide ions (O1, O2, and O3) and the oxide ion at the isolated site (O4) is not observed. The exchange of the oxide ions that are bonded to Si (O1, O2, and O3) suggests that they are the main diffusion species in oxide-ion conductivity.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Oxygen-17 nuclear magnetic resonance measurements on apatite-type lanthanum silicate (La9.33(SiO4)6O2)

et al. 2012

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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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“…[5] Single crystals had been grown for the RE 9.33 (SiO 4 ) 6 O 2 with RE=Pr, Nd and Sm by the floating zone method. [6][7][8][9][10] Their oxide ion conductivity was anisotropic, i.e. the conductivity parallel to c-axis in their hexagonal lattice was about one order of magnitude larger than that perpendicular to c-axis.…”

Section: Introductionmentioning

confidence: 99%

Oxide ion conduction mechanism in RE9.33(SiO4)6O2 and Sr2RE8(SiO4)6O2 (RE=La, Nd) from neutron powder diffraction

et al. 2006

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Oxide ion conduction mechanism was clarified by Rietveld and MEM analysis for both RE 9.33 (SiO 4 ) 6 O 2 and Sr 2 RE 8 (SiO 4 ) 6 O 2 (RE = La and Nd) in high purity using neutron powder diffraction data collected at room temperature. All compounds had an apatite type structure in space group P6 3 /m. There was neither site splitting nor interstitial site of oxide ion. RE 9.33 (SiO 4 ) 6 O 2 had cation vacancies only at 4f site. In Sr 2 RE 8 (SiO 4 ) 6 O 2 , the 4f sites were fully occupied by strontium and rare earth with a molar ratio of 1:1. Oxide ion at hexagonal channel site had large displacement along c-axis in RE 9.33 (SiO 4 ) 6 O 2 . The large displacement is induced by cooperative rotation of SiO 4 tetrahedra around rare earth in 4f site through oxide ion polyhedra around another rare earth in 6h site. The displacement, enhanced by a vacancy in the 4f site, is directly related to the oxide ion conduction in RE 9.33 (SiO 4 ) 6 O 2 .2

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Oxide ionic conductivity of apatite type Nd9·33(SiO4)6O2 single crystal

Cited by 172 publications

References 7 publications

Oxygen-17 nuclear magnetic resonance measurements on apatite-type lanthanum silicate (La9.33(SiO4)6O2)

Oxygen-17 nuclear magnetic resonance measurements on apatite-type lanthanum silicate (La9.33(SiO4)6O2)

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

Oxide ion conduction mechanism in RE9.33(SiO4)6O2 and Sr2RE8(SiO4)6O2 (RE=La, Nd) from neutron powder diffraction

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