Li Xiaoshuang, Li Chao, Gong Pifu, Lin Zheshuai, Yao Jiyong, Wu Yicheng
Center for Crystal Research and Development, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China and Key Laboratory of Functional Crystals and Laser Technology, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
Dalton Trans. 2016 Jan 14;45(2):532-8. doi: 10.1039/c5dt03682h.
Three new chalcogenides, namely NaGaGe3Se8, K3Ga3Ge7S20, and K3Ga3Ge7Se20, of an A-Ga-Ge-Q (A = Na, K; Q = S, Se) system were obtained for the first time. They crystallize into two different new structures, albeit both in the monoclinic space group P21/c. NaGaGe3Se8 has a layered structure consisting of two dimensional M4Se8 layers separated by Na(+) cations, while the structures of K3Ga3Ge7Q20 (Q = S, Se) are constructed by incompletely isolated quasi-2D M10Q21 layers, leading to large channels loosely occupied by K(+) cations. Interestingly, thermal analysis indicates that the three title compounds are all congruent-melting compounds, which is uncommon for quaternary compounds, and makes bulk crystal growth using the Bridgman technique possible. UV-vis-NIR spectroscopy measurements reveal that the optical band gaps of the three compounds are 2.35, 3.25, and 2.23 eV. In addition, the electronic structure calculations on NaGaGe3Se8 show that the band gap is mainly determined by the GaSe4 and GeSe4 groups.
首次获得了A-Ga-Ge-Q（A = Na，K；Q = S，Se）体系的三种新型硫族化物，即NaGaGe3Se8、K3Ga3Ge7S20和K3Ga3Ge7Se20。它们结晶为两种不同的新结构，尽管二者均属于单斜空间群P21/c。NaGaGe3Se8具有层状结构，由被Na(+)阳离子隔开的二维M4Se8层组成，而K3Ga3Ge7Q20（Q = S，Se）的结构则由不完全孤立的准二维M10Q21层构成，形成了由K(+)阳离子松散占据的大通道。有趣的是，热分析表明这三种标题化合物均为一致熔融化合物，这对于四元化合物而言并不常见，使得使用布里奇曼技术进行块状晶体生长成为可能。紫外-可见-近红外光谱测量表明，这三种化合物的光学带隙分别为2.35、3.25和2.23 eV。此外，对NaGaGe3Se8的电子结构计算表明，带隙主要由GaSe4和GeSe4基团决定。
