Synthesis and ionic conduction of apatite-type materials

Tao, Shanwen; Irvine, John T. S.

doi:10.1007/bf02374158

Cited by 29 publications

(24 citation statements)

References 31 publications

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“…With sol-gel powders, sintered pellets with relative density of 92% are achieved at 1400 8C with a heating rate of 100 8C h À1 and sintered for 2 h. This result is very interesting because, for oxyapatite powders synthesized by wet route chemistry, best densification values at 1500 8C were of about 74% [8]. The solution we have chosen to increase the density is to introduce an attrition-milling step for 2 h after calcination at 1000 8C of powders.…”

Section: Processing Of Powders To Prepare Ceramicsmentioning

confidence: 99%

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New chemical route based on sol–gel process for the synthesis of oxyapatite La9.33Si6O26

Célérier

Laberty

Ansart

et al. 2006

Ceramics International

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OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. AbstractThe aim of this paper is to advance in the field of the development of low-cost synthesis techniques easy to transfer at an industrial scale for electrolyte functional materials in intermediate temperature solid oxide fuel cells (IT-SOFC). We developed an original sol-gel route to synthesize La 9.33 Si 6 O 26 oxides. This approach is straightforward, inexpensive, versatile and it produces pure powders with controlled size and morphology. Via sol-gel route, crystallization temperature of such phases are drastically reduced: 800 8C in comparison with 1500 8C in solid-state conventional routes. The dependance of the nature of the phases was studied by varying several parameters as the hydrolysis rate, the volumetric ratio of catalyst to TEOS and the silicon concentration. All these parameters affect the homogeneity of the gel and thus, the purity of the oxides obtained after heat treatment in air. These oxyapatite materials have particle size of about 100 nm after heat treatment at 1000 8C. The use of these powders for ceramic processing allows a decrease of the sintering temperature of more than 200 8C.

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Section: Processing Of Powders To Prepare Ceramicsmentioning

confidence: 99%

“…), however, they are lower at high temperatures [1][2][3][4][5][6][7][8][9]. These results have been correlated to the structure of these materials [10][11][12][13][14].…”

mentioning

confidence: 99%

New chemical route based on sol–gel process for the synthesis of oxyapatite La9.33Si6O26

Célérier

Laberty

Ansart

et al. 2006

Ceramics International

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“…The first studies detailing the relation between · t and normalized oxygen partial pressure, p O2 from 1 to 10 ¹20 were published by Arikawa et al 146) and Tao et al 147) in 2000. However, the La 10 (SiO 4 ) 6 O 3 ceramic samples in both studies contained impurity phases.…”

Section: )mentioning

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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“…8) [25][26][27][28]. The conduction mechanism is related to the translational hopping of sodium ions along the c axis of the unit cell from ordinary lattice sites in interstitial sites and back again, which are the only candidates for such a condition process.…”

Section: Conductivity Datamentioning

confidence: 99%

X-ray structure refinement, vibrational spectroscopy, and ionic conductivity of Na0.11Ca9.64Sm0.23(PO4)6F2

Boujelbene

Mhiri

2014

Ionics

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The present paper is interested in the study of compounds from the apatite family, which is an apatite structure of individual rare earth substituted fluorapatite. In fact, an Sm-Bearing fluorapatite Ca 10-2y Na y Sm y (PO 4 ) 6 A 2 with x=0.11 and y=0.23 has been synthesized by solidstate reaction and characterized by X-ray powder diffraction. The site occupancies of substituents are 0.01091 for Sm and 0.02601 for Na in the Ca(1) position and 0.05317 for Sm in the Ca(2) position. Besides, the observed frequencies in the Raman and infrared spectra were explained and discussed on the basis of unit cell group analyses and in comparison with fluorapatite and other fluorapatites. In addition to the proton conduction, the possibility of a Na + contribution to the conductivity in the high-temperature phase is proposed. The highest overall conductivity values were found at σ 475°C =2.03×10−5 S cm −1 and Ea=0.60 eV.

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Synthesis and ionic conduction of apatite-type materials

Cited by 29 publications

References 31 publications

New chemical route based on sol–gel process for the synthesis of oxyapatite La9.33Si6O26

New chemical route based on sol–gel process for the synthesis of oxyapatite La9.33Si6O26

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

X-ray structure refinement, vibrational spectroscopy, and ionic conductivity of Na0.11Ca9.64Sm0.23(PO4)6F2

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