Three new compounds in the AE-Si-P (AE = Sr, Eu, Ba) systems are reported. Sr 2 SiP 4 and Eu 2 SiP 4 , the first members of their respective ternary systems, are isostructural to previously reported Ba 2 SiP 4 and crystallize in the noncentrosymmetric I42d (no. 122) space group. Ba 4 Si 3 P 8 crystallizes in the new structure type, in P2 1 /c (no. 14) space group, mP-120 Pearson symbol, Wyckoff sequence e 30 . In the crystal structures of Sr 2 SiP 4 and Eu 2 SiP 4 all SiP 4 tetrahedral building blocks are connected via formation of P-P bonds forming a 242 three-dimensional framework. In the crystal structure of Ba 4 Si 3 P 8 , Si-P tetrahedral chains formed by corner-sharing, edge-sharing, and P-P bonds are surrounded by Ba cations. This results in a quasi-onedimensional structure. Electronic structure calculations and UV/Vis measurements suggest that the AE 2 SiP 4 (AE = Sr, Eu, Ba) are direct bandgap semiconductors with bandgaps of ca. 1.4 eV and have potential for thermoelectric applications. duced crystal structures are noncentrosymmetric, for example the II-IV-V 2 chalcopyrite family (II = Mg, Zn, Cd; IV = Si, Ge, Sn; V = P, As, Sb), leading to their intensive study for nonlinear optical applications.

Three new strontium phosphide-halides, Sr 2 P 7 X (X = Cl, Br, and I) were synthesized and structurally characterized by single-crystal X-ray diffraction. In the crystal structure of all three compounds, strontium cations and halogen anions are present together with heptaphosphanortricyclane, P 7 3-, clusters. Sr 2 P 7 Br and Sr 2 P 7 I are isostructural and crystallize in a new structure type in the chiral cubic space group

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The synthesis, structural characterization, and optical properties of the binary Zintl phases of α-EuP3, β-EuP3, EuP2, and α-K4P6 are reported in this study. These crystal structures demonstrate the versatility of P fragments with dimensionality varying from 0D (P6 rings in α-K4P6) to 1D chains (EuP2) to 2D layers (both EuP3). EuP2 is isostructural to previously reported SrP2 and BaP2 compounds. The thermal stabilities of the EuP2 and both EuP3 phases were determined using differential scanning calorimetry (DSC), with melting temperatures of 1086 K for the diphosphide and 1143 K for the triphosphides. Diffuse reflectance spectroscopy indicated that EuP2 is an indirect semiconductor with a direct bandgap of 1.12(5) eV and a smaller indirect one, less than 1 eV. Both EuP3 compounds had bandgaps smaller than 1 eV.

Sr2P7I is prepared by solid state reaction of a stoichiometric mixture of the elements (evacuated silica tube, 973 K, 140 h) and Sr2P7Cl and Sr2P7Br are obtained from the reaction of Sr, red P, and SrBr (or SrCl) in the molar ratio of 3:14:1 under similar annealing conditions.