Converse Elizabeth Sobalvarro, Li Jun, Mullins Austin C, LaBarre Patrick G, Ramirez Arthur P, Subramanian M A
Department of Chemistry. Oregon State University, Corvallis, Oregon 97331, United States.
Department of Physics, University of California, Santa Cruz, California 95064, United States.
Inorg Chem. 2020 Oct 5;59(19):14141-14151. doi: 10.1021/acs.inorgchem.0c01901. Epub 2020 Sep 18.
Solid solutions with the formula of BiA'RuO (A' = Mg, Ca, Sr; 0 ≤ ≤ 0.2 for Mg, 0 ≤ ≤ 1 for Ca, and 0 ≤ ≤ 0.5 for Sr) have been synthesized and characterized. The crystal structures for these phases are found to be in the pyrochlore family, crystallizing in the cubic space group 3̅ with complex A/A' cation coordination environments. The Bi cation is found to be off-center from the ideal position because of a lone-pair distortion, while the positions of the substituted A' cations vary based on the size and ionicity. The neutron structure refinements reveal a similar propensity to off-center regarding Ca and Sr, while Mg features the largest static displacement of up to 0.48 Å. Interestingly, this is one of only two known pyrochlores with Mg located in an 8-coordinated site. The average Ru oxidation state for each substitution is found to increase, and charge compensates for the lower divalent A' substitution. The solid solutions show temperature-independent resistance across the series with small changes in magnitude that scale with the amount of substitution, while displaying Pauli paramagnetic behavior throughout.
已合成并表征了化学式为BiA'RuO的固溶体（A' = Mg、Ca、Sr；Mg的0 ≤ ≤ 0.2，Ca的0 ≤ ≤ 1，Sr的0 ≤ ≤ 0.5）。发现这些相的晶体结构属于烧绿石族，在立方空间群3̅中结晶，具有复杂的A/A'阳离子配位环境。由于孤对畸变，发现Bi阳离子偏离理想位置，而取代的A'阳离子的位置根据尺寸和离子性而变化。中子结构精修显示，Ca和Sr也有类似的偏离中心倾向，而Mg的最大静态位移高达0.48 Å。有趣的是，这是仅有的两种已知烧绿石之一，其中Mg位于8配位位点。发现每次取代的平均Ru氧化态增加，电荷补偿了较低价态的二价A'取代。该固溶体在整个系列中表现出与温度无关的电阻，其大小有微小变化，且与取代量成比例，同时在整个过程中表现出泡利顺磁行为。
