First-Principles Analyses of Electronic Structure of Multiferroic Nd Doped BiFeO3 Solid Solution

BiFeO
₃
(BFO) and Bi
_0.95
Nd
_0.05
FeO
₃
(B-Nd) ceramics were prepared by solid state reaction method[1]. In the perovskite type structure ABO
₃
, the substitution of Bi
³⁺
by Nd
³⁺
was identified on the A-site[2]. Crystal refinememts(from XRD in Fig. 1(a)) and STEM in Fig. 1(b)/HRTEM(Scanning and High-resolution transmission electron microscopy)with the multislice methods reveal a
R
3c space group with lattice parameters of a
_BFO
= 5.48 Å, α
_BFO
=59.90°, and a
_B-Nd
=5.64 Å, α
_B-Nd
=59.82° for BFO and B-Nd, respectively. For Nd doped BFO, the photovoltaic effect was markedly improved, where the maximum power-conversion efficiency increased around 2 order due to the reduced optical band gap, and, reduced leakage current density as Nd substitutes the Bi sites, resulting in a structural distortion, reducing the Bi deficiency [3]. The optically measured band gap are 2.24eV and 2.204eV for BFO and B-Nd, which are consistent reasonably well with the calculated results based on Vienna ab initio simulation package(VASP) [4], [5] following L(S)DA+U methods. In Figs. 1(c) and (d), the calculated band gap of B-Nd is 2.091eV which is smaller than the simulated value 2.271eV of BFO.