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@ARTICLE{Jia:860286,
      author       = {Jia, Chun-Lin and Jin, Lei and Chen, Yue-Hua and Urban,
                      Knut and Wang, Hong},
      title        = {{A}tomic-scale evidence for displacive disorder in bismuth
                      zinc niobate pyrochlore},
      journal      = {Ultramicroscopy},
      volume       = {192},
      issn         = {0304-3991},
      address      = {Amsterdam},
      publisher    = {Elsevier Science},
      reportid     = {FZJ-2019-01061},
      pages        = {57 - 68},
      year         = {2018},
      abstract     = {Pyrochlores characterized by the chemical formula A2B2O7
                      form an extended class of materials with interesting
                      physical and chemical properties. The compound
                      Bi1.5ZnNb1.5O7 is prototypical. Its excellent dielectric
                      properties make it attractive, e.g. for capacitors, tunable
                      microwave devices and electric-energy storage equipment.
                      Bi1.5ZnNb1.5O7 shows an intriguing frequency-dispersive
                      dielectric relaxation at 50 K ≤ T ≤ 250 K,
                      which has been studied intensively but is still not fully
                      understood. In this first study on a pyrochlore by
                      atomic-resolution transmission electron microscopy we
                      observe the Bi atoms on A sites since, due to their low
                      nuclear charge, the contribution of Zn atoms to the contrast
                      of these sites is negligible. We find in our and [112]
                      oriented images that the position of the atomic intensity
                      maxima do not coincide with the projected Wyckoff positions
                      of the basic pyrochlore lattice. This supplies atomic-scale
                      evidence for displacive disorder on split A-type sites. The
                      Bi atoms are sessile, only occasionally we observe in time
                      sequences of images jumps between individual split-site
                      positions. The apertaining jump rate of the order of
                      0.1–1 Hz is by ten orders of magnitude lower than the
                      values derived in the literature from Arrhenius plots of the
                      low-temperature dielectric relaxation data. It is argued
                      that these jumps are radiation induced. Therefore our
                      observations are ruling out a contribution of Bi-atom jumps
                      to low-temperature dielectric A sites-related relaxation. It
                      is suggested that this relaxation is mediated by jumps of Zn
                      atoms.},
      cin          = {ER-C-1},
      ddc          = {570},
      cid          = {I:(DE-Juel1)ER-C-1-20170209},
      pnm          = {143 - Controlling Configuration-Based Phenomena (POF3-143)},
      pid          = {G:(DE-HGF)POF3-143},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:29890501},
      UT           = {WOS:000437102000008},
      doi          = {10.1016/j.ultramic.2018.05.009},
      url          = {https://juser.fz-juelich.de/record/860286},
}