Os4+ Instability in the Pyrochlore Structure: Tl2-xBixOs2O7-y.,Inorganic Chemistry

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Os4+ Instability in the Pyrochlore Structure: Tl2-xBixOs2O7-y.
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2020-01-07 , DOI: 10.1021/acs.inorgchem.9b02939
Elizabeth Sobalvarro Converse ₁ , Jun Li ₁ , Daniel Haskel ₂ , Patrick G LaBarre ₃ , Arthur P Ramirez ₃ , M A Subramanian ₁

Affiliation

Osmium-containing oxides are rare due to the difficulty in stabilizing complex structures with a fixed stoichiometry and metastability of the phases. Bismuth-substituted thallium osmate pyrochlore samples, Tl2-xBixOs2O7-y, were synthesized using solid-state reactions where the solubility limit was found to be approximately x = 1.4. Members of this solid solution were characterized by their structural, electronic, magnetic, and thermal properties to understand the influence of Bi3+ substitution on the ground state. The Os-containing pyrochlores crystallize in the ideal cubic pyrochlore structure (Fd3m), and the lattice parameter a was found to slightly increase as a function of Bi content. A possible interplay between structure and cation valence states was explored using both neutron powder diffraction and X-ray absorption spectroscopy, suggesting that a combination of Os4+/Os5+ and Tl1+/Tl3+ mixed valency throughout the solid solution allows for the stabilization of the pyrochlore structure. The system is metallic for the entire solid solution and predominantly exhibits temperature-independent paramagnetism. Specific heat measurements show an enhanced Sommerfeld coefficient, a possible flat-band signature. This system gave insight into the bonding preferences of Os, indicating a dependence on high oxidation states and mixed valence for the stability of complex structures.

中文翻译：

烧绿石结构中的Os4 +不稳定性：Tl2-xBixOs2O7-y。

由于难以稳定具有固定的化学计量比和相的亚稳性的复杂结构，因此含的氧化物很少见。使用固溶反应合成了铋取代的酸os盐烧绿石样品Tl2-xBixOs2O7-y，发现溶解度极限约为x = 1.4。该固溶体的成员以其结构，电子，磁性和热性质为特征，以了解Bi3 +取代对基态的影响。含Os的烧绿石以理想的立方烧绿石结构（Fd3m）结晶，并且发现晶格参数a随Bi含量的增加而略有增加。使用中子粉末衍射和X射线吸收光谱研究了结构和阳离子价态之间可能存在的相互作用，这表明在整个固溶体中，Os4 + / Os5 +和Tl1 + / Tl3 +混合化合价可稳定烧绿石结构。该系统对于整个固溶体都是金属的，并且主要表现出与温度无关的顺磁性。比热测量显示出更高的Sommerfeld系数，这可能是平带信号。该系统深入了解了Os的键合偏好，表明了对于复杂结构的稳定性，其依赖于高氧化态和混合化合价。比热测量显示出更高的Sommerfeld系数，这可能是平带信号。该系统深入了解了Os的键合偏好，表明了对于复杂结构的稳定性，其依赖于高氧化态和混合价。比热测量显示出更高的Sommerfeld系数，这可能是平带信号。该系统深入了解了Os的键合偏好，表明了对于复杂结构的稳定性，其依赖于高氧化态和混合价。

更新日期：2020-01-07

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