Effect of the dopant nature on the conductivity of oxygen overstoichiometric oxyapatites with controlled microstructures

Guillot, Stéphanie; Beaudet-Savignat, Sophie; Lambert, S.; Roussel, Pascal; Vannier, Rose‐Noëlle

doi:10.1016/j.ssi.2010.12.005

Cited by 13 publications

(9 citation statements)

References 43 publications

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“…The formed phases were analyzed using samples 16 and 17 (see table 4 and figure 2). Although these compositions agree with the previous reports on the formation of oxyapatite single phase [7][8][9]13], a La 2 SiO 5 phase as well as the oxyapatite phase were segregated as shown in figure 5. The La 2 SiO 5 segregation was due to the lower reaction temperature in this study (1773 K) than in the previous studies (1923-1873 K).…”

Section: Oxyapatite Solid Solutionsupporting

confidence: 91%

“…In particular, a metastable oxyapatite phase would be formed when samples contained the liquid phase at the annealing temperature and were cooled to lower temperature as discussed above. On the other hand, a high reaction temperature above 1823 K has been employed to synthesize the oxyapatite single phase by a conventional solid state reaction method [1][2][3][4][5][6][7][8][9][10][11][12][13]. However, the possibility of a metastable oxyapatite phase has been overlooked; hence, further research is necessary to clarify the effect of the liquid phase on the oxyapatite formation, formation of metastable oxyapatite and sintering behavior.…”

Section: Liquid-phase-related Region and Phases Formed At Room Tempermentioning

confidence: 99%

“…The compositional features of MgO-doped lanthanum silicate oxyapatites can be emphasized by plotting their elemental content on a Gibbs triangular graph [4][5][6][7][8][9][10][11][12][13][14] (figure 1). The oxyapatite phase is located on two compositional lines: horizontal line A that corresponds to the substitution of MgO for SiO 2 at a fixed LaO 1.5 concentration, and line B along which MgO was substituted for LaO 1.5 at a fixed SiO 2 concentration.…”

Section: Introductionmentioning

confidence: 99%

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Phase relationships in the quasi-ternary LaO_1.5–SiO₂–MgO system at 1773 K

Kobayashi

Sakka

2012

Science and Technology of Advanced Materials

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Phase relationships in the LaO 1.5 -SiO 2 -MgO quasi-ternary system at 1773 K were investigated by powder x-ray diffraction (XRD) analysis applying single-and multiple-phase Rietveld methods. Most of the formed phases satisfied the Gibbs' phase rule, except for the samples containing LaO 1.5 and a liquid phase at 1773 K. The detection of segregated MgO phases was difficult in the XRD profiles of the compositional samples around the oxyapatite single phase because the MgO peaks were weak and heavily overlapped by peaks from the oxyapatite and La(OH) 3 phases. The solid solubility limit of MgO in oxyapatite was determined not only from the chemical composition of the oxyapatite phase, which was confirmed by XRD, but also from several phase boundary compositions among the two-phase and three-phase regions based on the Gibbs' phase rule. Formation of a liquid phase at 1773 K was observed in a wide range of compositions and considered when constructing the phase diagram.

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Section: Oxyapatite Solid Solutionsupporting

confidence: 91%

Section: Liquid-phase-related Region and Phases Formed At Room Tempermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Phase relationships in the quasi-ternary LaO_1.5–SiO₂–MgO system at 1773 K

Kobayashi

Sakka

2012

Science and Technology of Advanced Materials

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“…The studies show an enhancement of the ionic conduction in the La 10−x (Si,Al) 6 O 26±ı series, where Al doping is compensated by the La-site vacancies without oxygen content variations [6,22,24] or the oxygen excess without La-cation vacancies [25,27]. Experiments on alkaline earth doping studies in samples containing oxygen excess show that the conductivity of barium doped La 9 Ba(SiO 4 ) 6 O 2.5 , which is cation stoichiometric but contains an oxygen excess, is high [28][29][30]. There are clear evidences that oxygen over-stoichiometry is responsible for the good oxide conductivity properties.…”

Section: Introductionmentioning

confidence: 99%

Sinterability and conductivity of barium doped aluminium lanthanum oxyapatite La9.5Ba0.5Si5.5Al0.5O26.5 electrolyte of solid oxide fuel cells

Cao

2012

Journal of Alloys and Compounds

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“…Guillot et al analyzed the crystal structure of La 9 Ba(SiO 4 ) 6 O 2.5 by the Rietveld method using NPD patterns obtained at 293, 973, 1073, and 1173 K. 98) With respect to the data at 293 K, the structure parameters of La 9.83 Si 5.5 Al 0.5 O 26.5 and La 10 Si 5.5 Mg 0.5 -O 26.5 were also presented. All compounds were refined using the structure model with space group P6 3 /m.…”

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

confidence: 99%

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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Effect of the dopant nature on the conductivity of oxygen overstoichiometric oxyapatites with controlled microstructures

Cited by 13 publications

References 43 publications

Phase relationships in the quasi-ternary LaO_1.5–SiO₂–MgO system at 1773 K

Phase relationships in the quasi-ternary LaO_1.5–SiO₂–MgO system at 1773 K

Sinterability and conductivity of barium doped aluminium lanthanum oxyapatite La9.5Ba0.5Si5.5Al0.5O26.5 electrolyte of solid oxide fuel cells

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

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Effect of the dopant nature on the conductivity of oxygen overstoichiometric oxyapatites with controlled microstructures

Cited by 13 publications

References 43 publications

Phase relationships in the quasi-ternary LaO1.5–SiO2–MgO system at 1773 K

Phase relationships in the quasi-ternary LaO1.5–SiO2–MgO system at 1773 K

Sinterability and conductivity of barium doped aluminium lanthanum oxyapatite La9.5Ba0.5Si5.5Al0.5O26.5 electrolyte of solid oxide fuel cells

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

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Phase relationships in the quasi-ternary LaO_1.5–SiO₂–MgO system at 1773 K

Phase relationships in the quasi-ternary LaO_1.5–SiO₂–MgO system at 1773 K