Structure of oxide ion-conducting lanthanum oxyapatite, La9.33(SiO4)6O2

Okudera, Hiroki; Masubuchi, Yuuji; Kikkawa, Shinichi; Yoshiasa, Akira

doi:10.1016/j.ssi.2005.02.014

Cited by 112 publications

(108 citation statements)

References 12 publications

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“…The occupation preference of RE vacancies and strontium was observed at the RE1(4f ) site in all their compounds. Similar to Okudera's results, 55),56) the vacancy at the RE1(4f ) site appeared to be relaxed by the rotation of SiO 4 tetrahedra because anisotropic thermal displacements for the O1(6h), O2(6h), and O3(12i) sites of RE 9.33 42) and Masubuchi et al 67) reveals that the main differences are the anisotropic thermal displacements of the La1(4f ) site, and whether the interstitial oxygen site is within the unit cell. For anisotropic thermal displacement of the La1(4f ) site, an almost isotropic displacement was proposed by León-Reina et al However, anisotropic thermal displacement along the c-axis was proposed by Okudera et al 42) and Masubuchi et al 67) Examination of the anisotropic thermal-displacement parameters reveals slightly loose constraints at the La1(4f ) and O4 (2a) 71) They collected powder XRD and NPD patterns and refined the crystal-structure parameters using the Rietveld method.…”

Section: Crystal Structure Model After the Discovery Of Oxygen-ion Cosupporting

confidence: 73%

“…42) They determined that their sample was not a single phase but a two-phase mixture of La 9.33 (SiO 4 ) 6 O 2 as the major phase and La 2 SiO 5 (3.4 mass %) as minor impurity phase. With respect to the isotropic thermal-displacement parameters, correct constraints for the parameters were employed for the analysis.…”

Section: Crystal Structure Model After the Discovery Of Oxygen-ion Comentioning

confidence: 99%

“…8, we compare the diffraction patterns of La 9.33 -(SiO 4 ) 6 O 2 using the Sansom model (space group: P 3) and a typical apatite structure reported by Okudera et al 42) (space group: P6 3 /m). In the XRD patterns simulated using the RIETAN-FP software, 50) a distinguishable peak (001 peak) is observed at 2ª µ 12.3°.…”

Section: Crystal Structure Model After the Discovery Of Oxygen-ion Comentioning

confidence: 99%

“…Okudera et al 42) reported full crystal-structure data for La 9.33 -(SiO 4 ) 6 O 2 using single-crystal XRD analysis. They selected a spherical single grain from the sintered ceramics fabricated by heating under an infrared light using a floating-zone instrument.…”

Section: Crystal Structure Model After the Discovery Of Oxygen-ion Comentioning

confidence: 99%

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Research progress in nondoped lanthanoid silicate oxyapatites as new oxygen-ion conductors

Kobayashi

Sakka

2014

J. Ceram. Soc. Japan

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The discovery of oxygen-ion conductivity and changes in the crystal-structure model of nondoped lanthanum silicate oxyapatites are reviewed from the researches which led to the discovery to current work. The oxygen-ion conductivity of lanthanoid silicate oxyapatites was discovered by Nakayama et al., during development of new oxide lithium-ion conductors. Although samples with compositions of LiRESiO 4 (RE = La, Nd, Sm, Gd, Dy) were initially reported to be single phases with the same crystal structure, the accurate crystal structure of LiRESiO 4 was not clarified until later. The crystal structure determined from X-ray diffraction patterns of LiLnSiO 4 was revised as oxyapatite by another group. The chemical composition of the crystal phases in LiRESiO 4 was also revised to RE 10 Si 6 O 25 and/or RE 9.33 Si 6 O 24 . The discovery of oxygen-ion conductivity in these materials was confirmed when researchers noted that samples of RE 10 Si 6 O 25 , specifically, the samples without lithium, are electrically conducting. Furthermore, very high oxygen-ion conductivity in the direction parallel to c-axis was discovered after single crystals of RE 9.33 (SiO 4 ) 6 O 2 (RE = Nd, Pr, and Sm) were successfully grown. The crystal structure and defect models were also altered after the discovery of oxygen-ion conductivity. Although numerous reports related to the electrical conductivity of La 9.33+x (SiO 4 ) 6 O 2+3x/2 ceramics have appeared in the literature, clear dependences of the total conductivity on the cation nonstoichiometry (x) as well as the sintering temperature are still unclear because of large discrepancies in the reported data. Furthermore, the composition region, where the lanthanum silicate oxyapatite single phase is formed, is also still unclear because of the inconsistencies in the reported results.

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Section: Crystal Structure Model After the Discovery Of Oxygen-ion Cosupporting

confidence: 73%

Section: Crystal Structure Model After the Discovery Of Oxygen-ion Comentioning

confidence: 99%

Section: Crystal Structure Model After the Discovery Of Oxygen-ion Comentioning

confidence: 99%

Section: Crystal Structure Model After the Discovery Of Oxygen-ion Comentioning

confidence: 99%

See 2 more Smart Citations

Research progress in nondoped lanthanoid silicate oxyapatites as new oxygen-ion conductors

Kobayashi

Sakka

2014

J. Ceram. Soc. Japan

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“…However, X-ray diffraction analyses for the stoichiometric phase by Okudera et al did not detect the presence of interstitial oxygen ions and showed large anisotropy in O4-ion motion, which suggests the linear conduction pathway running through the O4 column. 13 They also supported the sinusoidal-like interstitial mechanism in the O4 channels, and also found the slightly different behavior of the moving interstitial oxygen ions (the "S N 2-type" process) between O4 channels, where the interstitial oxygen ions diffuse even normal to the c axis interacting with SiO 4 units. In contrast, Béchade et al applied static lattice simulations and the bond valence method for stoichiometric La 9.33 (SiO 4 ) 6 O 2 , and proposed the push-pull mechanism, where interstitial oxygen ions do not diffuse through the O4 channel independently but undergo cooperative movement with O4 ions.…”

Section: Introductionmentioning

confidence: 55%

Ionic conduction mechanisms of apatite-type lanthanum silicate and germanate from first principles

Matsunaga

2017

J. Ceram. Soc. Japan

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Ionic conduction mechanisms in apatite-type lanthanum silicate and germanate studied by first-principles calculations were reviewed, along with the ones previously proposed by experiments and atomistic simulations. It was found that the most stable interstitial oxygen sites in La 10 (SiO 4 ) 6 O 3 are located at the vicinity of the O4 column and the metastable sites are present between SiO 4 tetrahedra. In contrast, La 10 (GeO 4 ) 6 O 3 showed the most stable sites between GeO 4 tetrahedra, forming Ge 2 O 9 units. These can reasonably explain interstitial sites reported experimentally. The fundamental mechanism for ionic conduction in both systems is the interstitialcy mechanism, where interstitial oxygen ions and oxygen ions at regular lattice sites undergo cooperative motion through the lattices. In particular, the interstitialcy mechanism via Si/GeO 4 tetrahedra takes place by sequential bondforming and bond-breaking events between Si/Ge and oxygen ions, and play an important role to realize rapid ionic conduction.

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Synthesis of La_9.33Si₆O₂₆ Pore–Solid Nanoarchitectures via Epoxide‐Driven Sol–Gel Chemistry

Célérier¹,

Laberty-Robert²,

Long³

et al. 2006

Advanced Materials

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Silicate-based oxides are of interest as electrolytes and electrode materials in intermediate-temperature solid-oxide fuel cells (SOFCs). [1][2][3][4][5][6][7] We have developed a sol-gel-based strategy for the production of mesoporous, nanostructured, singlephase La 9.33 Si 6 O 26 apatite in an aerogel-type framework. Silicon alkoxides react with lanthanum(III) aqueous ions in alcohol solutions driven by a proton-scavenging agent, propylene oxide. Varying the means by which pore fluid is removed from the resultant lanthanum silicate gels yields three distinct pore-solid monolithic nanoarchitectures: aerogels, ambigels, and xerogels. The ambigel and aerogel nanoarchitectures exhibit high specific surface areas (from 285 to 408 m 2 g -1), aperiodic through-connected networks of mesopores, and covalently bonded networks of non-agglomerated nanoparticles. Calcination at relatively mild temperatures for this oxide (800°C) converts the amorphous gels to nanocrystalline apatite La 9.33 Si 6 O 26 . Although densified during calcination, the aerogel and ambigel nanoarchitectures retain porosity, high surface area, and limited particle agglomeration. Aerogels and related highly porous architectures are defined by a bonded three-dimensional network of nanoparticles, commingled with interconnected porosity. [8][9][10] The inherent structural characteristics of aerogels are highly beneficial for electrochemical applications, [9] where the high interfacial surface area enhances the kinetics of electrochemical reactions and the continuous mesoporous network facilitates the transport of molecules, ions, and nanoscale objects to the active electrode surface while the solid network of covalently linked nanoparticles promotes charge transport of electrons and ions. It is only recently that aerogel-like materials have been synthesized in electrically conductive, SOFC-relevant compositions and then characterized at operating temperatures. [11,12] An earlier sol-gel route to mixed La-Si oxides modified an acid-catalyzed silica sol-gel method by including lanthanum salts. [13,14] Investigation of a range of hydrolysis rates showed that only very narrow synthesis conditions led to apatite La 9.33 Si 6 O 26 upon calcination (800°C), [1] and impurity phases were common. Subsequent attempts to produce aerogels or ambigels (requiring washing steps with ethanol) led to amorphous oxides after calcination (1000°C), suggesting that this protocol generates a silica network with the lanthanum salt dispersed on its surface.[1]Our approach to synthesize lanthanum silicate nanoarchitectures is based on the initial formation of oligomers of La-O-Si by using epoxide-and alkoxide-driven hydrolysis and condensation reactions. This synthetic protocol is a modification of innovative methods reported by Gash et al. for the preparation of transition metal oxide aerogels. [15][16][17] This route was recently extended to mixed transition metal oxide aerogels [11,18] and nanocomposites of silica and metal oxide. [19,20] We obtain gels by mixing tetramethoxysi...

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Structure of oxide ion-conducting lanthanum oxyapatite, La9.33(SiO4)6O2

Cited by 112 publications

References 12 publications

Research progress in nondoped lanthanoid silicate oxyapatites as new oxygen-ion conductors

Research progress in nondoped lanthanoid silicate oxyapatites as new oxygen-ion conductors

Ionic conduction mechanisms of apatite-type lanthanum silicate and germanate from first principles

Synthesis of La_9.33Si₆O₂₆ Pore–Solid Nanoarchitectures via Epoxide‐Driven Sol–Gel Chemistry

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Structure of oxide ion-conducting lanthanum oxyapatite, La9.33(SiO4)6O2

Cited by 112 publications

References 12 publications

Research progress in nondoped lanthanoid silicate oxyapatites as new oxygen-ion conductors

Research progress in nondoped lanthanoid silicate oxyapatites as new oxygen-ion conductors

Ionic conduction mechanisms of apatite-type lanthanum silicate and germanate from first principles

Synthesis of La9.33Si6O26 Pore–Solid Nanoarchitectures via Epoxide‐Driven Sol–Gel Chemistry

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Product

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Synthesis of La_9.33Si₆O₂₆ Pore–Solid Nanoarchitectures via Epoxide‐Driven Sol–Gel Chemistry