Doping and Temperature Dependence of Raman Scattering of NdFeAsO1-xFx   (x=0.0, 0.1, 0.2) Superconductor
  Raman spectra of polycrystalline NdFeAsO1-xFx (x=0.0, 0.1, 0.2) compound have been systematically investigated as functions of temperature and fluorine concentration. Scanning electron microscopic and Raman microscopic characterization demonstrates that the polycrystalline samples mainly contain two phases, i.e. superconductor NdFeAsO1-xFx compound and a MnP-type FeAs phase, with dissimilar characteristic Raman bands. It was found that fluorine doping leads to structure disorder in the insulator Nd-O layers and high temperature coefficient of Fe-As vibrational mode. 
L. Zhang, T. Fujita, F. Chen, D. L. Feng, S. Maekawa, and M. W. Chen