Zhou Molin, Li Chao, Li Xiaoshuang, 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, P.R. China and University of Chinese Academy of Sciences, Beijing 100049, P.R. China.
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, P.R. China.
Dalton Trans. 2016 May 4;45(18):7627-33. doi: 10.1039/c6dt00143b.
Three new compounds (i.e., K2Sn2ZnSe6, Na2Ge2ZnSe6, and Na2In2GeSe6) with intriguing structural diversity and nonlinear optical properties were discovered for the first time. They crystallize in space groups P4/ncc, I4/mcm and Cc, respectively. In K2Sn2ZnSe6 and Na2Ge2ZnSe6, the [Sn(Ge)Se4] tetrahedra and [ZnSe4] tetrahedra are linked via edge-sharing to build up a 1D [Sn2ZnSe6] infinite chain separated by K(+)(Na(+)) cations along the c direction, while the structure of Na2In2GeSe6 is an interesting three-dimensional framework composed of [InSe4] and [GeSe4] tetrahedra via corner-sharing with Na(+) cations in the cavities. The experimental optical band gaps of these compounds were determined as 1.71(2) eV, 2.36(4) eV and 2.47(2) eV, respectively, according to UV-vis-NIR diffuse reflectance spectroscopy. Interestingly, in addition to the large band gap (1.80 eV for AgGaSe2, as a comparison), Na2In2GeSe6 exhibits phase-matchable nonlinear optical (NLO) properties with a powder second harmonic generation signal about 0.8 times that of AgGaS2. Moreover, Na2In2GeSe6 melts congruently at a rather low temperature of 671 °C, which suggests that bulk crystals can be easily obtained by the Bridgman-Stockbarger method. Our preliminary results indicate that Na2In2GeSe6 has promising applications in IR nonlinear optics.
首次发现了三种具有有趣结构多样性和非线性光学性质的新化合物（即K2Sn2ZnSe6、Na2Ge2ZnSe6和Na2In2GeSe6）。它们分别结晶于空间群P4/ncc、I4/mcm和Cc中。在K2Sn2ZnSe6和Na2Ge2ZnSe6中，[Sn(Ge)Se4]四面体和[ZnSe4]四面体通过共边连接，沿c方向构建了由K(+)(Na(+))阳离子隔开的一维[Sn2ZnSe6]无限链，而Na2In2GeSe6的结构是一个有趣的三维框架，由[InSe4]和[GeSe4]四面体通过与空穴中的Na(+)阳离子共角连接而成。根据紫外-可见-近红外漫反射光谱，这些化合物的实验光学带隙分别测定为1.71(2) eV、2.36(4) eV和2.47(2) eV。有趣的是，除了具有较大的带隙（作为对比，AgGaSe2的带隙为1.80 eV）外，Na2In2GeSe6还表现出相位匹配的非线性光学（NLO）性质，其粉末二次谐波产生信号约为AgGaS2的0.8倍。此外，Na2In2GeSe6在相当低的671 °C温度下完全熔融，这表明通过布里奇曼-斯托克巴杰方法可以很容易地获得块状晶体。我们的初步结果表明，Na2In2GeSe6在红外非线性光学方面具有广阔应用前景。
