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@INPROCEEDINGS{Sohn:817881,
      author       = {Sohn, Yoo Jung and Reppert, Thorsten and Sebold, Doris and
                      Finsterbusch, Martin and Guillon, Olivier},
      title        = {{N}eutron powder diffraction study of high {L}i-ion
                      conductive {L}i7-x{A}lx{L}a3{Z}r2{O}12},
      reportid     = {FZJ-2016-04487},
      year         = {2016},
      abstract     = {The garnet-type lithium oxides with the general formula
                      Li7La3Zr2O12 (LLZ) are promising candidates for
                      all-solid-state lithium batteries due to their high ionic
                      conductivity and electrochemical stability. The tetragonal
                      LLZ crystallizes in the space group I41/acd at room
                      temperature and exhibits a relatively low total Li-ionic
                      conductivity of ≈ 10-6 Scm-1 [1], whereas the
                      high-temperature cubic phase with the space group Ia-3d
                      gives an elevated total ionic conductivity of ≈ 10-4 Scm-1
                      [2]. Li-occupancy in the crystal structure plays a
                      significant role in the conduction, since Li-ion jump can
                      take place through the energetically favorable atom
                      positions that are only partially occupied [3, 4]. The
                      presence of vacancies in LLZ lowers the activation energy
                      and enhances Li-ionic conductivity. 20 mol $\%$
                      aluminum-doped LLZ was synthesized by solid state reaction
                      to stabilize the crystal structure, and hence to improve the
                      total ionic conductivity by increasing the number of
                      vacancies. The X-ray powder diffraction analysis shows a
                      mixture of tetragonal and cubic Al-doped LLZ with the weight
                      fraction ratio of almost 1:1. The impedance measurement on
                      this mixture compound revealed a high total ionic
                      conductivity of ≈ 10-4 Scm-1, despite of the presence of
                      the poorly conducting tetragonal phase. To elucidate this
                      phenomenon, neutron powder diffraction was performed on the
                      mixed phase Al-doped LLZ as well as on the pure tetragonal
                      one. Rietveld analysis was carried out to obtain detailed
                      crystal structure information, and a possible mechanism of
                      the Li-ion conduction was discussed according to its crystal
                      structure. [1] Awaka J., Kijima N., Hayakawa H., Akimoto J.
                      J. Solid State Chem. 2009, 182, 2046. [2] Murugan R.,
                      Thangadurai V., Weppner W. Angew. Chem. Int. Ed. 2007, 46,
                      7778.[3] Li Y., Han J., Wang C., Vogel S., Xie H., Xu M.,
                      Goodenough J. J. Power Sources 2012, 209, 278.[4] Meier K.,
                      Laino T., Curioni A. J. Phys. Chem. C. 2014, 118,
                      6668Keywords: neutron powder diffraction, crystal structure,
                      Li-ionic conductivity},
      month         = {Jun},
      date          = {2016-06-12},
      organization  = {The 15th European Powder Diffraction
                       Conference, Bari (Italy), 12 Jun 2016 -
                       15 Jun 2016},
      subtyp        = {Other},
      cin          = {IEK-1 / JARA-ENERGY},
      cid          = {I:(DE-Juel1)IEK-1-20101013 / $I:(DE-82)080011_20140620$},
      pnm          = {131 - Electrochemical Storage (POF3-131) / HITEC -
                      Helmholtz Interdisciplinary Doctoral Training in Energy and
                      Climate Research (HITEC) (HITEC-20170406)},
      pid          = {G:(DE-HGF)POF3-131 / G:(DE-Juel1)HITEC-20170406},
      typ          = {PUB:(DE-HGF)6},
      url          = {https://juser.fz-juelich.de/record/817881},
}