X-ray Absorption Spectroscopy Study of Nd-doped Bi₄Ti₃O₁₂ Dielectrics

We investigated the influence of neodymium doping on the chemistry and the local electronic structures in Bi₄Ti₃O₁₂ by using soft X-ray absorption spectroscopy (XAS). The Nd M_4,5-edge XAS spectra of Bi_4-xNd_xTi₃O₁₂ (x = 0, 0.25, 0.5, and 1) showed that all the Nd ions had a valence of +3. This suggests that the Nd³⁺ ions can indeed substitute for the Bi³⁺ ions. The Ti L_2,3-edge XAS spectra further showed that the Ti-O coordination was robustly maintained for all values of x in a manner similar to that for amorphous TiO₂. Moreover, the conduction band energies estimated from the O K-edge XAS were similar to each other. Meanwhile, the electrical conductivity decreased noticeably with increasing Nd concentration. Therefore, we conclude that the lowering of the leakage current due to Nd doping is not relevant to certain structural evolutions within the ferroelectric domains.