@article{13520,
  abstract     = {{Atomistic simulations in the framework of the density functional theory have been used to model morphologic and vibrational properties of lithium niobate–lithium tantalate mixed crystals as a function of the [Nb]/[Ta] ratio. Structural parameters such as the crystal volume and the lattice parameters a and c vary roughly linearly from LiTaO3 to LiNbO3, showing only minor deviations from the Vegard behavior. Our ab initio calculations demonstrate that the TO1, TO2 and TO4 vibrational modes become harder with increasing Nb concentration. TO3 becomes softer with increasing Nb content, instead. Furthermore, the investigated zone center A1 -TO phonon modes are characterized by a pronounced stoichiometry dependence. Frequency shifts as large as 30 cm−1 are expected as the [Nb]/[Ta] ratio grows from 0 to 1. Therefore, spectroscopic techniques sensitive to the A1 modes (such as Raman spectroscopy), can be employed for a direct and non-destructive determination of the crystal composition.}},
  author       = {{Sanna, Simone and Riefer, A. and Neufeld, Sergej and Schmidt, Wolf Gero and Berth, Gerhard and Rüsing, Michael and Widhalm, A. and Zrenner, Artur}},
  issn         = {{0015-0193}},
  journal      = {{Ferroelectrics}},
  keywords     = {{Ferroelectrics, vibrational properties, LiNbO3, LiTaO3, mixed crystals}},
  number       = {{1}},
  pages        = {{63--68}},
  title        = {{{Vibrational Fingerprints of LiNbO3-LiTaO3Mixed Crystals}}},
  doi          = {{10.1080/00150193.2013.821893}},
  volume       = {{447}},
  year         = {{2013}},
}

@inproceedings{4380,
  abstract     = {{The structural and vibrational properties of lithium niobate (LN) – lithium tantalate (LT) mixed crystals (LNT, LiNb1-xTaxO3) are investigated over the whole composition range by first-principles simulations. The crystal volume grows roughly linearly from LT to LN, whereby the lattice parameters a and c show minor deviations from the Vegard behavior between the end compounds, LiNbO3 and LiTaO3. Our calculations in the framework of the density functional theory show the TO1, TO2 and TO4-modes to become harder with increasing Nb concentration. TO3 becomes softer with increasing Nb content, instead. The frequency shifts of the zone center A1-TO phonon modes for crystals with different compositions are found to be as large as 30 cm-1. Raman spectroscopy, which is sensitive to the A1 modes, can be therefore employed to determine the crystal composition.}},
  author       = {{Sanna, Simone and Riefer, Arthur and Neufeld, Sergej and Schmidt, Wolf Gero and Berth, Gerhard and Widhalm, Alex and Zrenner, Artur}},
  booktitle    = {{Proceedings of ISAF-ECAPD-PFM 2012}},
  keywords     = {{Ferroelectrics, Vibrational properties, LiNbO3, LiTaO3, Mixed Crystals}},
  location     = {{Aveiro, Portugal}},
  title        = {{{Vibrational fingerprints of LiNbO3-LiTaO3 mixed crystals}}},
  year         = {{2012}},
}

@article{4377,
  abstract     = {{Confocal Raman spectroscopy was performed as an archetype imaging method to study the ferroelectric domain structure of periodically poled lithium niobate. More precisely, the linkage out of spatial resolution and spectral information proved itself as very useful. Here a specific modulation of the Raman lines by the local variation of polarity and a non-symmetric measuring-signal across the domain structure were found, which allows for imaging of domain boundaries as well as oppositely orientated domains. The high potential of this method is demonstrated by the visualization of the ferroelectric domain structures based on various phonon modes.}},
  author       = {{Berth, Gerhard and Hahn, Wjatscheslaw and Wiedemeier, Volker and Zrenner, Artur and Sanna, Simone and Schmidt, Wolf Gero}},
  issn         = {{0015-0193}},
  journal      = {{Ferroelectrics}},
  keywords     = {{Raman spectroscopy, ferroelectric domains, LiNbO3, confocal imaging}},
  number       = {{1}},
  pages        = {{44--48}},
  publisher    = {{Informa UK Limited}},
  title        = {{{Imaging of the Ferroelectric Domain Structures by Confocal Raman Spectroscopy}}},
  doi          = {{10.1080/00150193.2011.594774}},
  volume       = {{420}},
  year         = {{2011}},
}

@article{4553,
  abstract     = {{We present results on ferroelectric micro-domains obtained by confocal second harmonic microscopy. The high potential of this technique is demonstrated by imaging periodic ferroelectric domain structures in the surface of planar X-cut lithium niobate (LN) and in the body of ridges fabricated by plasma etching on X-cut LN as well. In both cases the measured second harmonic signal reveals a strong contrast between inverted and non-inverted domain sections. This enabled a depth-resolved non-destructive tomography of micro-domains in ridge structures in all three dimensions.}},
  author       = {{Berth, Gerhard and Wiedemeier, Volker and Hüsch, Klaus-Peter and Gui, Li and Hu, Hui and Sohler, Wolfgang and Zrenner, Artur}},
  issn         = {{0015-0193}},
  journal      = {{Ferroelectrics}},
  keywords     = {{Nonlinear microscopy, ferroelectric micro-domains, confocal imaging, LiNbO3}},
  number       = {{1}},
  pages        = {{132--141}},
  publisher    = {{Informa UK Limited}},
  title        = {{{Imaging of Ferroelectric Micro-Domains in X-Cut Lithium Niobate by Confocal Second Harmonic Microscopy}}},
  doi          = {{10.1080/00150190902993267}},
  volume       = {{389}},
  year         = {{2009}},
}