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Exploring new nonlinear optical (NLO) materials with high laser-induced damage threshold (LIDT) in the infrared (IR) region is vital for the development of technologies relying on tunable laser sys...

In this study, two quaternary diamond-like semiconductors (DLSs) in the Cu-Zn-Ge-Se system, the known Cu2ZnGeSe4 (also referred to as CZGSe) and the new Cu4ZnGe2Se7, are compared in terms of their crystal structures, electronic structures and physicochemical properties. Both compounds were prepared by high-temperature, solid-state synthesis at 800 °C. Single crystal X-ray diffraction was used to determine the structure of Cu4ZnGe2Se7. The structures of both Cu2ZnGeSe4 and Cu4ZnGe2Se7 can be considered as derivatives of cubic diamond. Cu4ZnGe2Se7, with a reduced symmetry due to the cation ordering pattern, adopts the Cu4NiSi2S7 structure type, with space group C2. The corner-sharing tetrahedra in Cu4ZnGe2Se7 are slightly distorted because the charge for some of the S2- anions is not compensated by the first-nearest-neighbor cations. Rietveld refinements using synchrotron X-ray powder diffraction data were used to assess the phase purity of the samples and confirm the bulk structural behavior. Diffuse reflectance UV/Vis/NIR spectroscopy shows that Cu2ZnGeSe4 and Cu4ZnGe2Se7 have direct optical bandgaps of 1.38 and 0.91 eV, respectively. Electronic structure calculations implementing density functional theory confirm the direct bandgap for Cu4ZnGe2Se7, with a calculated value of 0.62 eV. Both compounds are air stable, thermally stable up to relatively high temperatures, undergo phase transitions and have wide windows of optical clarity. The Kurtz-Perry powder technique was used to determine the second harmonic generation (SHG) responses using a commercial AgGaSe2 standard. While Cu4ZnGe2Se7 displays a weak SHG response, Cu2ZnGeSe4 exhibits a response that is greater than several benchmark materials, with a large SHG coefficient, χ ( 2 ) , of 43 ± 6 pm/V at λ = 2900 nm.

Novel quaternary lanthanide-substituted oxides of stoichiometry Ln x Y 2−x Ti 2 O 7 (where Ln is lanthanum, neodymium, samarium, gadolinium, or ytterbium) were prepared by traditional high-temperature, solid-state techniques and characterized by X-ray powder diffraction. Samples with nominal values of x up to 1.0 were attempted. The well-studied ternary cubic pyrochlore compound yttrium titanium oxide (Y 2 Ti 2 O 7 , space group Fd- 3 m , Z = 8), served as a parent structural framework in which Ln 3+ cations were substituted on the Y 3+ site. Laboratory-grade X-ray powder diffraction data revealed pure quaternary pyrochlore phases for Ln x Y 2−x Ti 2 O 7 with x ≤ 0.2. Pyrochlore phase purity was verified by Rietveld analysis using high-resolution synchrotron X-ray powder diffraction data when x ≤ 0.2, however, for La 3+ substitution specifically, pure quaternary pyrochlore formed at x

While X-ray powder diffraction (XRPD) is a fundamental analytical technique used by solid-state laboratories across a breadth of disciplines, it is still underrepresented in most undergraduate curricula. In this work, we incorporate XRPD analysis into an inquiry-based project that requires students to identify the crystalline component(s) of familiar household products. Centering the project on materials which students encounter in their everyday lives helps to demystify the technique, making it accessible to everyone with a basic understanding of crystallinity and unit cells. In an XRPD study, each crystalline component generates a unique set of peaks in the diffractogram. Comparing the collected diffractogram to a library of diffractograms for known crystalline materials allows students to identify the crystalline components in their unknown. Students must determine for themselves the chemical compositions of the possible unknowns, and link their findings back to the analysis of the collected data. Init...