Institute of Materials Engineering, Australian Nuclear Science and Technology Organisation, Kirrawee DC, NSW, Australia.
J Phys Condens Matter. 2010 Nov 10;22(44):445401. doi: 10.1088/0953-8984/22/44/445401. Epub 2010 Oct 22.
We have carried out Ce L- and Mn K-edge x-ray absorption near edge structure (XANES) measurements to experimentally determine the oxidation states of both Ce and Mn in (Sr(1 - x)Ce(x))MnO(3) (x = 0.1-0.4). It was found that although Ce is predominantly 4 + at low doping levels (x = 0.1 and 0.15), the Ce valency decreases with increasing Ce doping (reaching a value of around 3.5 + at x = 0.4). The average Mn oxidation state decreases with the increase of Ce content, with the percentage of Jahn-Teller active Mn(3+) ions increasing from 26% (x = 0.1) to 57% (x = 0.4). Precise structural parameters were also obtained from high resolution neutron diffraction studies for samples with x = 0.1-0.3. The crystal structure remains tetragonal in I4/mcm for x ≤ 0.3. The octahedral tilt angle increases with increasing Ce content, but the distortion of the MnO(6) octahedra is reduced significantly at x ≥ 0.2 due to a transition from long-range ordered Jahn-Teller distortions to incoherent static distortions.
我们进行了 Ce L 和 Mn K 边缘的 X 射线吸收近边缘结构（XANES）测量，以实验确定（Sr(1 - x)Ce(x))MnO(3)（x = 0.1-0.4）中 Ce 和 Mn 的氧化态。结果发现，尽管 Ce 在低掺杂水平（x = 0.1 和 0.15）下主要为 4 +，但随着 Ce 掺杂的增加，Ce 价态降低（在 x = 0.4 时达到约 3.5 +）。随着 Ce 含量的增加，平均 Mn 氧化态降低， Jahn-Teller 活性 Mn(3+)离子的百分比从 26%（x = 0.1）增加到 57%（x = 0.4）。还对 x = 0.1-0.3 的样品进行了高分辨率中子衍射研究，获得了精确的结构参数。对于 x ≤ 0.3，晶体结构保持在 I4/mcm 中为四方晶系。八面体倾斜角随 Ce 含量的增加而增加，但由于长程有序 Jahn-Teller 畸变向非相干静态畸变的转变，在 x ≥ 0.2 时 MnO(6)八面体的畸变显著降低。
