title: Cs2GeB4O9: a new second-order nonlinear-optical crystal.
abstract: 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.
authors: 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.
authors: Xiang
authors: X
authors: Xu
authors: Chun-Li
authors: CL
authors: Hu
authors: Fang
authors: F
authors: Kong
authors: Jian-Han
authors: JH
authors: Zhang
authors: Jiang-Gao
authors: JG
authors: Mao
authors: Junliang
authors: J
authors: Sun