State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, People's Republic of China.
Inorg Chem. 2013 May 20;52(10):5831-7. doi: 10.1021/ic302774h. Epub 2013 May 6.
A new alkali-metal borogermanate with noncentrosymmetric structure, namely, Cs2GeB4O9, has been discovered, and a large crystal with dimensions of 20 × 16 × 8 mm(3) has been grown by a high-temperature top-seeded solution method using Cs2O-B2O3 as a flux. The compound crystallizes in the tetragonal space group I4 with a = b = 6.8063(2) Å, c = 9.9523(7) Å, V = 461.05(4) Å(3), and Z = 2. It features a three-dimensional anionic open framework based on GeO4 tetrahedra and B4O9 clusters that are interconnected via corner-sharing, forming one-dimensional channels of nine-/ten-membered rings along the a and b axes, which are occupied by Cs(+) cations. Cs2GeB4O9 exhibits a very high thermal stability with a melting point of 849 °C, and it possesses a short-wavelength absorption edge onset at 198 nm determined by UV-vis transmission spectroscopy measurements on a slab of polished crystal. Powder second-harmonic generation (SHG) measurement on sieved crystals reveals that Cs2GeB4O9 is a type I phase-matchable material with a strong SHG response of about 2.8 × KH2PO4. The preliminary investigation indicates that Cs2GeB4O9 is a new promising second-order nonlinear-optical crystalline material.
一种具有非中心对称结构的新型碱金属锗硼酸盐，即 Cs2GeB4O9，已被发现。通过高温顶部籽晶溶液法，使用 Cs2O-B2O3 作为助熔剂，生长出尺寸为 20×16×8mm³的大晶体。该化合物属于四方晶系，空间群为 I4，a=b=6.8063(2)Å，c=9.9523(7)Å，V=461.05(4)ų，Z=2。它具有基于 GeO4 四面体和 B4O9 簇的三维阴离子开放式骨架，通过角共享相互连接，形成沿 a 和 b 轴的一维 9-/10-元环通道，这些通道被 Cs(+)阳离子占据。Cs2GeB4O9 表现出非常高的热稳定性，熔点为 849°C，其短波长吸收边缘起始于 198nm，这是通过对抛光晶体薄片进行紫外-可见透射光谱测量得出的。对筛分晶体进行的粉末二次谐波产生 (SHG) 测量表明，Cs2GeB4O9 是一种 I 型相位匹配材料，具有约 2.8×KH2PO4 的强 SHG 响应。初步研究表明，Cs2GeB4O9 是一种有前途的新型二阶非线性光学晶体材料。
