Department of Chemistry . Oregon State University , Corvallis , Oregon 97331 , United States.
Advanced Photon Source , Argonne National Laboratory , Lemont , Illinois 60439 , United States.
Inorg Chem. 2020 Jan 21;59(2):1227-1233. doi: 10.1021/acs.inorgchem.9b02939. Epub 2020 Jan 7.
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, TlBiOsO, were synthesized using solid-state reactions where the solubility limit was found to be approximately = 1.4. Members of this solid solution were characterized by their structural, electronic, magnetic, and thermal properties to understand the influence of Bi substitution on the ground state. The Os-containing pyrochlores crystallize in the ideal cubic pyrochlore structure (3), and the lattice parameter 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 Os/Os and Tl/Tl 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.
含锇氧化物由于难以稳定具有固定化学计量比的复杂结构和相的亚稳性而很少见。使用固态反应合成了取代铋的铊锇氧焦绿石样品 TlBiOsO，其中发现溶解度极限约为 = 1.4。该固溶体的成员通过其结构、电子、磁和热性质进行了表征，以了解 Bi 取代对基态的影响。含 Os 的焦绿石在理想的立方焦绿石结构 (3) 中结晶，晶格参数随着 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的可能相互作用，表明整个固溶体中存在 Os/Os 和 Tl/Tl 混合价态的相互作用，使得焦绿石结构得以稳定。整个固溶体都是金属的，主要表现出温度独立的顺磁性。比热测量显示增强的 Sommerfeld 系数，可能是平带特征。该系统深入了解了 Os 的成键偏好，表明对高氧化态和混合价态的依赖是复杂结构稳定性的关键。
