New Metal Chalcogenides Ba(4)CuGa(5)Q(12) (Q = S, Se) Displaying Strong Infrared Nonlinear Optical Response

Abstract

A series of new metal chalcogenides Ba(4)CuGa(5)Q(12) (Q = S, S0.75Se0.25, Se) were synthesized using KBr flux at 750 degrees C. The three compounds are isostructural and adopt the noncentrosymmetric space group P (4) over bar2(1)c. Crystal data are as follows: Ba(4)CuGa(5)Q(12), 1, a = 13.040(1) angstrom, c = 6.304(1) angstrom, and Z = 2; Ba4CuGa5S9.00(1)Se2.92(1), 2, a = 13.1585(2) angstrom, c = 6.3520(2) angstrom, and Z = 2; Ba4CuGa5Se12, 3, a = 13.598(1) angstrom, c = 6.527(1) angstrom, and Z = 2. The three-dimensional framework in 1 is constructed by infinite columns (1)(infinity)[CuGa4S10](7-) that surround the discrete GaS4 tetrahedra situated on a (4) over bar -axis. The discrete GaS4 tetrahedra on the stacking (112) planes and canted oriented edge-sharing CuS4 tetrahedra within the columns may account for the occurrence of strong second-harmonic generation (SHG) responses. Compounds 1-3 are transparent in the mid-infrared range and have the absorption edges at 2.82, 2.05, and 1.45 eV, respectively. The new nonlinear optical (NLO) materials are type-I nonphase matching at 693 nm and display strong SHG intensities that are similar to 2.7, similar to 2.6, and similar to 1.1 times that of AgGaSe2 at 808 nm. Raman spectroscopic characterization of the compounds is reported.