La4(Si5.2Ge2.8O18)(TeO3)4 and La2(Si6O13)(TeO3)2: Intergrowth of the lanthanum(III) tellurite layer with the XO4 (X=Si/Ge) tetrahedral layer

Breaking through the "3.0 eV wall" of energy band gap in mid-infrared nonlinear optical rare earth chalcogenides by charge-transfer engineering

Increasing the energy band gap under the premise to maintain a large nonlinear optical (NLO) response is a challenging issue for the exploration and molecular design of mid-infrared nonlinear optical crystals. Utilizing a charge-transfer engineering method, we designed and synthesized a rare earth chalcogenide, KYGeS₄. With an NLO effect as large as that in AgGaS₂, KYGeS₄ breaks through the limitation of energy band gap, i.e., the "3.0 eV wall", in NLO rare earth chalcogenides, and thus exhibits an excellent comprehensive NLO performance. First-principles electronic structure analysis demonstrates that the large band gap in KYGeS₄ is ascribed to the decreased covalency of Y-S bonds by transferring charge from [YS₇] to [GeS₄] polyhedra. The charge-transfer engineering strategy would have significant implications for the exploration of good-performance NLO crystals.

Accidental formation of Gd₄(SiO₄)₂OTe: crystal structure and spectroscopic properties

Designing new functional materials with increasingly complex compositions is of current interest in science and technology. Complex rare-earth-based chalcogenides have specific thermal, electrical, magnetic and optical properties. Tetragadolinium bis[tetraoxidosilicate(IV)] oxide telluride, Gd4(SiO4)2OTe, was obtained accidentally while studying the Gd2Te3-Cu2Te system. The crystal structure was determined by means of single-crystal X-ray diffraction. The compound crystallizes in the space group Pnma. Three symmetry-independent gadolinium sites were determined. The excitation and emission spectra were collected at room temperature and at 10 K. Gd4(SiO4)2OTe appears to be a promising optical material when doped with rare-earth ions.

Synthesis, structures, and properties of two magnesium silicate fluorides Mg5(SiO4)2F2 and Mg3SiO4F2

The structural differences of title compounds were investigated, and the related physical properties and theoretical calculations were also reported.