Single crystals of the polytellurides RETe1.8 of gadolinium, terbium, and dysprosium were prepared by chemical vapor transport and alkali metal halide flux reactions. To determine proper synthesis conditions for the desired target composition, the binary phase diagram Gd‐Te was evaluated by CalPhaD methods. The compounds are isostructural to SmTe1.8 and crystallize in space group P4/n (no. 85) with lattice parameters of a = 966.10(4), 960.00(3), and 957.33(2) pm and c = 1794.15(10), 1785.77(6), and 1779.38(5) pm for GdTe1.8, TbTe1.8 and DyTe1.8, respectively. The structures consist of puckered [RETe] double slabs and planar telluride layers composed of Te2 dumbbells and linear Te3 units in accordance with ELI‐D based bonding analyses. The latter can be understood as a Te34– anion. GdTe1.8 is a semiconductor with a bandgap of 0.19 eV/0.17 eV (experimental/calculated). Magnetization data confirm trivalent RE ions and indicate antiferromagnetic order at TN = 12 K for TbTe1.8 and TN = 9.8 K for DyTe1.8, whereas GdTe1.8 remains paramagnetic down to 2 K.
Technological interest in the design of solid state materials has stimulated recent research into the development of mild molten polychalcophosphate salt fluxes for the synthesis of complex, multinary rare earth and transition metal thiophosphate compounds. The reaction pathways from elemental or metal sulfide sources can be influenced by a variety of often interdependent factors of which counter cation sizes and charges, basicity, and temperature are of paramount importance. In rare earth and transition metal containing thiophosphates the dominating structural building units are tetrahedral [PS 4 ] 3À or ethane-like [P 2 S 6 ] 4À anions. Hierarchical topological relations between individual members of structural families of the type A m M n P y S z (A ¼ alkali metal, M ¼ rare earth or transition metal) can be established that provide a detailed insight into probable mechanisms of formation. The findings enable the development of guidelines for the employment of suitable counter cations in controlling the condensation of small species into chains, layers or frameworks.
Inspired by the oxide SrB4O7with the largest known band gap among all borate crystals, the chalcogenide BaAl4S7with similar structure may possess attractive NLO properties.
The reactions of Ti with in situ formed polythiophosphate fluxes of A(2)S(3) (A = Rb, Cs), P(2)S(5), and S at 500 degrees C result in the formation of two new quaternary titanium thiophosphates with compositions Rb(3)Ti(3)(P(4)S(13))(PS(4))(3) (1) and Cs(2)Ti(2)(P(2)S(8))(PS(4))(2) (2). Rb(3)Ti(3)(P(4)S(13))(PS(4))(3) (1) crystallizes in the chiral hexagonal space group P6(3) (No. 173) with lattice parameters a = 18.2475(9) Angstrom, c = 6.8687(3) Angstrom, V = 1980.7(2) Angstrom(3), Z = 2. Cs(2)Ti(2)(P(2)S(8))(PS(4))(2) (2) crystallizes in the noncentrosymmetric monoclinic space group Cc (No. 9) with a = 21.9709(14) Angstrom, b = 6.9093(3) Angstrom, c = 17.1489(10) Angstrom, beta = 98.79(1) degrees, V = 2572.7(2) Angstrom(3), Z = 4. In the structure of 1 TiS(6) octahedra, three [PS(4)] tetrahedra, and the hitherto unknown [P(4)S(13)](6-) anion are joined to form two different types of helical chains. These chains are connected yielding two different helical tunnels being directed along [001]. The tunnels are occupied by the Rb+ ions. The [P(4)S(13)](6-) anion is generated by three [PS(4)] tetrahedra sharing corners with one [PS(4)] group in the center of the starlike anion. The P atoms of the three [PS(4)] tetrahedra attached to the central [PS(4)] group define an equilateral triangle. The [P(4)S(13)](6-) anion may be regarded as a new member of the [P(n)S(3n+1)]((n+2)-) series. The structure of Cs(2)Ti(2)(P(2)S(8))(PS(4))(2) (2) consists of the one-dimensional polar tunnels containing the Cs(+) cations. The rare [P(2)S(8)](4-) anion which is composed of two [PS(4)] tetrahedra joined by a S(2)(2-) anion is a fundamental building unit in the structure of 2. One-dimensional undulated chains being directed along [100] are joined by [PS(4)] tetrahedra to form the three-dimensional network with polar tunnels running along [010]. The compounds are characterized with IR, Raman spectroscopy, and UV/vis diffuse reflectance spectroscopy.
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