The dependence of 10 Dq crystal field parameter for Mn4+ (3d3 configuration) and the magnitude of 7F1 level splitting for Eu3+ (4f6 configuration) on pyrochlore compositions
The dependence of 10 Dq crystal field parameter for Mn4+ (3d3 configuration) and the magnitude of 7F1 level splitting for Eu3+ (4f6 configuration) on pyrochlore compositions
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DOI：
10.1016/j.optmat.2012.07.026
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发表时间：
2012-12
影响因子：
3.9
通讯作者：
A. Srivastava;M. Brik
中科院分区：
文献类型：
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作者：
A. Srivastava;M. Brik
测定了六配位Mn4+离子在焦绿石Ln2Sn2O7（Ln=Lu3+, Y3+, Gd3+）中的激发光谱，考察了晶体场分裂参数（10 Dq）对Mn4+ - o48f2 -距离的影响。所得结果完全符合静电点电荷模型的预期，10 Dq随着Mn4+ - o48f2 -距离的减小而逐渐增大。对Eu3+(4f6)和Mn4+(3d3)离子在焦绿石Ln2(Ti,Sn)2O7（Ln=Lu3+, Y3+, Gd3+）中的行为进行了比较研究。结果表明，Mn4+和Eu3+离子在Ln2Sn2O7（Ln=Lu3+, Y3+, Gd3+）族材料中的晶体场强度是反相关的。因此，对于3d3构型的Mn4+离子，晶体场强度随着Ln3+离子半径的减小而增大，而对于4f6构型的Eu3+离子，晶体场强度随着Ln3+离子半径的增大而增大。然而，当y2sn2o7晶格中的Sn4+离子被Ti4+离子取代时，晶体场强度降低，以至于暴露的Mn4+3d3电子和屏蔽的Eu3+4f6电子的行为开始相似。这些结果可以用配体（O48f2-）和活化剂（Mn4+和Eu3+）阳离子之间的共价混合变化来解释，这是由Ln2(Ti,Sn) 2o7晶格中的Ln3+、Sn4+和Ti4+离子对O48f2电子密度的竞争所驱动的。
The excitation spectra of the six-coordinated Mn4+ion in the pyrochlores Ln2Sn2O7(Ln=Lu3+, Y3+, and Gd3+) have been determined to examine the variation in the crystal field splitting parameter (10 Dq) on the Mn4+–O48f2-distance. The results obtained are entirely consistent with the expectation of the electrostatic point charge model since 10 Dq progressively increase with decreasing Mn4+–O48f2-distance. A comparative study pertaining to the behavior of the Eu3+(4f6) and Mn4+(3d3) ions in the pyrochlores, Ln2(Ti,Sn)2O7(Ln=Lu3+, Y3+, and Gd3+) is presented. The results show that the crystal-field strength that are experienced by the Mn4+and Eu3+ions in the Ln2Sn2O7(Ln=Lu3+, Y3+, and Gd3+) family of materials, are anti-correlated. Thus, for the Mn4+ion with 3d3configuration, the crystal-field strength increases with decreasing ionic radii of the Ln3+cation, while for the Eu3+ion with 4f6configuration, an increase with increasing ionic radii of the Ln3+cation is observed. However, when the Sn4+ion of the Y2Sn2O7lattice are replaced by the Ti4+ion, the crystal-field strength is reduced to the extent that the exposed Mn4+3d3electrons and the screened Eu3+4f6electrons start to behave similarly. These results are explained by the variations in the covalent mixing between the ligand (O48f2-) and the activator (Mn4+and Eu3+) cations, which is driven by the competition for the O48f2-electron density by the Ln3+, Sn4+, and Ti4+ions of the Ln2(Ti,Sn)2O7lattice.