title: Apatite germanates doped with tungsten: synthesis, structure, and conductivity.
abstract: High oxygen content apatite germanates, La(10)Ge(6-x)W(x)O(27+x), have been prepared by doping on the Ge site with W. In addition to increasing the oxygen content, this doping strategy is shown to result in stabilisation of the hexagonal lattice, and yield high conductivities. Structural studies of La(10)Ge(5.5)W(0.5)O(27.5) show that the interstitial oxygen sites are associated to a different degree with the Ge/WO(4) tetrahedra, leading to five coordinate Ge/W and significant disorder for the oxygen sites associated with these units. Raman spectroscopy studies suggest that in the case of the WO(5) units, the interstitial oxygen is more tightly bonded and therefore not as mobile as in the case of the GeO(5) units, thus not contributing significantly to the conduction process.
authors.affiliation: Instituto de Ciencia de Materiales de Aragón, C.S.I.C.-Universidad de Zaragoza, E-50.009, Zaragoza, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Orera
authors.forename: T
authors.initials: T
authors.lastname: Baikie
authors.forename: E
authors.initials: E
authors.lastname: Kendrick
authors.forename: J F
authors.initials: JF
authors.lastname: Shin
authors.forename: S
authors.initials: S
authors.lastname: Pramana
authors.forename: R
authors.initials: R
authors.lastname: Smith
authors.forename: T J
authors.initials: TJ
authors.lastname: White
authors.forename: M L
authors.initials: ML
authors.lastname: Sanjuán
authors.forename: P R
authors.initials: PR
authors.lastname: Slater
mesh_terms: D001031:Apatites / Q000138:chemical synthesis* / Q000737:chemistry; D004553:Electric Conductivity; D005857:Germanium / Q000737:chemistry*; D007811:Lanthanum / Q000737:chemistry; D008958:Models, Molecular; D010087:Oxides / Q000737:chemistry*; D013059:Spectrum Analysis, Raman; D014414:Tungsten / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D001031:Apatites; D010087:Oxides; D005857:Germanium; C103829:lanthanum oxide; C040516:germanium oxide; D007811:Lanthanum; C511604:tungsten oxide; D014414:Tungsten