The semiconductors Li(2)CdGeS(4) and Li(2)CdSnS(4), which are of interest for their nonlinear optical properties, were synthesized using high-temperature solid-state and polychalcogenide flux syntheses. Both compounds were found to crystallize in Pmn2(1), with R1 (for all data) = 1.93% and 1.86% for Li(2)CdGeS(4) and Li(2)CdSnS(4), respectively. The structures of both compounds are diamond-like with the tetrahedra pointing in the same direction along the c axis. The alignment of the tetrahedra results in the structure lacking an inversion center, a prerequisite for second-harmonic generation (SHG). A modified Kurtz nonlinear optical powder technique was used to determine the SHG responses of both compounds. Li(2)CdGeS(4) displayed a type I phase-matchable response of approximately 70x alpha-quartz, while Li(2)CdSnS(4) displayed a type I non-phase-matchable response of approximately 100x alpha-quartz. Diffuse-reflectance spectroscopy was used to determine band gaps of 3.10 and 3.26 eV for Li(2)CdGeS(4) and Li(2)CdSnS(4), respectively.
Polymorphism and Second harmonic generation in a novel diamond-like semiconductor: Li 2 MnSnS 4 , Journal of Solid State Chemistry, http://dx. Abstract:High-temperature, solid-state synthesis in the Li2MnSnS4 system led to the discovery of two new polymorphic compounds that were analyzed using single crystal X-ray diffraction. The α-polymorph crystallizes in Pna21 with the lithium cobalt (II) silicate, Li2CoSiO4, structure type, where Z=4, R1=0.0349 and wR2=0.0514 for all data. The β-polymorph possesses the wurtz-kesterite structure type, crystallizing in Pn with Z=2, R1=0.0423, and wR2=0.0901 for all data. Rietveld refinement of synchrotron X-ray powder diffraction was utilized to quantify the phase fractions of the polymorphs in the reaction products. The α/β-Li2MnSnS4 mixture exhibits an absorption edge of ~2.6-3.0 eV, a wide region of optical transparency in the mid-to far-IR, and moderate SHG activity over the fundamental range of 1.1-2.1 μm. Calculations using density functional theory indicate that the ground state energies and electronic structures for α-and β-Li2MnSnS4, as well as the hypothetical polymorph, γ-Li2MnSnS4 with the wurtz-stannite structure type, are highly similar.
Optical properties D 6000Second-Harmonic Generation and Crystal Structure of the Diamond-Like Semiconductors Li 2 CdGeS 4 and Li 2 CdSnS 4 . -The title compounds are obtained from polysulfide fluxes at 650°C (96 h) starting with a Li2S/Cd/Ge/S (2:1:1:8) mixture for Li2CdGeS4 and a Li2S/Cd/Sn/S (4:1:1:16) mixture for Li2CdSnS4. Both compounds crystallize in the orthorhombic space group Pmn21 with Z = 2 (single crystal XRD). The structures are diamond-like with the tetrahedra pointing in the same direction along the c axis. The alignment of the tetrahedra results in a structure lacking an inversion center, a prerequisite for second-harmonic generation (SHG). A modified Kurtz nonlinear optical powder technique is used to determine the SHG responses of both compounds. Li2CdGeS4 displays a type I phase-matchable response of approximately 70 times that of α-SiO2, while Li2CdSnS4 exhibits a type I non-phase-matchable response of approximately 100 times that of α-SiO 2 . The bandgaps of Li 2 CdGeS 4 and Li 2 CdSnS 4 are determined to be 3.10 and 3.26 eV, respectively. -(LEKSE, J. W.; MOREAU, M. A.; MCNERNY, K. L.; YEON, J.; HALASYAMANI, P. S.; AITKEN*, J. A.; Inorg. Chem. 48 (2009) 16, 7516-7518; Dep. Chem. Biochem., Duquesne Univ., Pittsburgh, PA 15282, USA; Eng.) -Schramke 43-007
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