Raman spectrum, crystal structure and superconductivity in Zn/Fe-doped GdBa2Cu3O7−δ systems

The M-doped GdBa2Cu3−xMxO7−δ (MZn, Fe) systems have been systemically investigated by means of XRD, SEM and Raman spectroscopy. The results show that the samples undergo an orthorhombic–tetragonal (O–T) phase transition near x = 0.10 by Fe ions doping. Although all the Zn-doped samples remain orthorhombic structure, the changes of the lattice parameters in the Zn-doped samples may induce a structural distortion because of Jahn–Teller effect. The crystallite appearances alter perceptibly with the Fe/Zn doping contents. Meanwhile, the changes of the typical Raman models are discussed. The research has found that the Raman modes present distinctive behaviors by Zn or Fe ions doping, which strongly depend on the crystal structure, especially on O–T phase transition. The effects of structure phase transition and the changes of the phonon vibration on the mechanism of electrical transport properties by Fe and Zn doping in different Cu sites are also discussed.

► The M-doped GdBa2Cu3−xMxO7−δ (M = Zn, Fe) systems have been systemically investigated.
► The Fe-doped samples undergo an orthorhombic–tetragonal phase transition near x = 0.10.
► The Zn-doped samples remain orthorhombic structure.
► The Raman modes present distinctive behaviors by Zn or Fe ions doping.