CHEN Qiao-Ling;LUO Min;LIN Chen-Sheng
College of Mathematics and Physics, Fujian University of Technology;Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences;Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences
A new carbonate nonlinear optical (NLO) material, KNa 5Ca 5(CO 3) 8, was successfully synthesized by mild hydrothermal method. It crystallizes in hexagonal space group (P63 mc) with lattice parameters a = b = 1.007 86(4) and c = 1.262 56(8) nm ( Z = 2). The structure of KNa 5Ca 5(CO 3) 8 can be described as standing-on-edge [CO 3] groups connecting the adjacent infinite [CaCO 3] ∞ layers in the a-b plane to construct a framework with four types of channels running parallel to . K, Na and [Na 0.67Ca 0.33] atoms reside in the tunnels. In the structure, the flat-lying [CO 3] groups in two successive layers present an opposite orientation. This arrangement is negative for NLO susceptibilities. The macroscopic of SHG effects, however, originated from the standing-on-edge [CO 3] group along c axis. It is regrettable that the standing-on-edge [C3O 3] and [C4O 3] groups are almost arranged oppositely to the c direction, which weakens the SHG contribution from the standing-on-edge [CO 3] groups. The measurement of second harmonic generation (SHG) by the method adapted from Kurtz and Perry indicates that the compound is phase-matchable in visible region and exhibits moderate SHG response about 1.2 times higher than that of KH 2PO 4. In addition, the UV-Vis-NIR diffuse reflection spectral measurements indicate that KNa 5Ca 5(CO 3) 8 has a large optical gap about 5.95 eV. Moreover, the first-principles electronic structure calculations show that the CO 3 groups play an important role in the total SHG response. Therefore, our data suggest that the new compound as NLO material may have potential applications in the UV region.
UV;carbonates;nonlinear optical crystal;crystal growth
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