α- and β-A₂Hg₃M₂S₈ (A = K, Rb; M = Ge, Sn):  Polar Quaternary Chalcogenides with Strong Nonlinear Optical Response

Abstract

The closely related phases alpha- and beta-A(2)Hg(3)M(2)S(8) (A = K, Rb; M = Ge, Sn) have been discovered using the alkali polychalcogenide flux method and are described in detail. They present new structure types with a polar noncentrosymmetric crystallographic motif and strong nonlinear second-harmonic generation (SHG) properties. The alpha-allotropic form crystallizes in the orthorhombic space group Aba2 with a = 19.082(2) A, b = 9.551(1) A, c = 8.2871(8) A for the K(2)Hg(3)Ge(2)S(8) analogue, and a = 19.563(2) A, b = 9.853(1) A, c = 8.467(1) A for the K(2)Hg(3)Sn(2)S(8) analogue. The beta-form crystallizes in the monoclinic space group C2 with a = 9.5948(7) A, b = 8.3608(6) A, c = 9.6638(7) A, beta = 94.637 degrees for the K(2)Hg(3)Ge(2)S(8) analogue. The thermal stability and optical and spectroscopic properties of these compounds are reported along with detailed solubility and crystal growth studies of the alpha-Kappa(2)Hg(3)Ge(2)S(8) in K(2)S(8) flux. These materials are wide gap semiconductors with band gaps at approximately 2.40 and approximately 2.64 eV for the Sn and Ge analogues, respectively. Below the band gap the materials exhibit a very wide transmission range to electromagnetic radiation up to approximately 14 microm. alpha-K(2)Hg(3)Ge(2)S(8) shows anisotropic thermal expansion coefficients. SHG measurements, performed with a direct phase-matched method, showed very high nonlinear coefficient d(eff) for beta-K(2)Hg(3)Ge(2)S(8) approaching 20 pm/V. Crystals of K(2)Hg(3)Ge(2)S(8) are robust to air exposure and have a high laser-damage threshold.

Syntheses, crystal structures, and characterization of As(III) and As(V) thioarsenates, [Mn2(phen)(AsIII2S5)]n and [Mn3(phen)3(AsvS4)2]n·nH2O

“…There is currently a great deal of interest in the synthesis, structures, and properties of new chalcogenide-based materials due to their potential applications, for example in optoelectronic materials, molecule-discriminating catalysis, ion-exchangers, nonlinear optical (NLO) materials, chemical sensing applications, and semiconductors [1][2][3][4][5]. Particularly, crystalline chalcogenides exemplified by a large number of quaternary/ternary M/E 0 /E clusters and open frameworks (M ¼ transition metal, E 0 ¼ heavy group 13-15 element, E ¼ S, Se, Te) with intriguing applications, ranging from semiconductors to gas separation, have received increasing attention at present [6][7].…”

Experimental and theoretical studies of Sn3−δPbδBi2Se6 (δ=0.0–0.7)

“…Chalcogenide compounds formed by combinations of such ions usually exhibit complex crystal structures and semiconducting properties with a narrow band gap, and are promising materials for nonlinear optics [4], ferroelectrics [5], and thermoelectrics [6][7][8]. Materials in this class contain various coordination environments constructed from M 2 + (M= Sn, Pb) and M 3 + (M =Sb, Bi) centers and Se 2 À ions assembled into a structure similar to that of lillianite [9].…”

“…The structures of the lillianite-type chalcogenides can be denoted as L(n,n 0 ), in which n and n 0 are the numbers of metal sites in the octahedral chains of the two alternating slabs; the different members of the lillianite series vary in the thickness of the NaCl-type blocks. Many naturally occurring minerals and synthetic lillianite-type or special case of Pavonite series [P(N,1)] chalcogenides have been studied, including PbBi 4 S 7 [L(2,1)] [16]; CuBi 5 S 8 [L(3,1)] [17]; Cu 3.21 Bi 4.79 S 9 [L(4,1)] [18]; AgBi 3 S 5 [L(5,1)] [19]; Pb 3 Bi 2 S 6 [9,20], AgPbBi 3 S 6 [21], and AgPbSb 3 S 6 [L(4,4)] [22]; Ag 5 Pb 8 Bi 13 S 30 [L(4,7)] [23]; Pb 6 Bi 2 S 9 [24] and K 0.54 Sn 4.92 Bi 2.54 Se 9 [L(7,7)] [25]; Ag 3 Bi 7 S 12 [L(7,1)] [26]; KSn 5 Bi 5 Se 13 [L(4,5)] [25]; Ag 7 Pb 6 Bi 15 S 32 [L (4,8)] [27]; Ag 7 Pb 10 Bi 15 S 36 [L (5,9)] [10]; and Ag 12.5 Pb 15 Bi 20.5 S 52 [L (11,11)] [11]. Most of the above lillianite and Pavonite type chalcogenides are sulfosalts; only a few selenides have been reported.…”

Recent advances on second-order NLO materials based on metal iodates

“…Currently, the most widely used second-order NLO materials are inorganic crystals such as ␤-BaB 2 O 4 (BBO), LiB 3 O 5 (LBO), KH 2 PO 4 (KDP), KTiOPO 4 (KTP), LiNbO 3 (LN), ZnGeP 2 and AgGaSe 2 [6][7][8][9][10][11][12][13].…”