High Pressure Properties of a Ba-Cu-Zn-P Clathrate-I.

The high pressure properties of the novel tetrel-free clathrate, Ba₈Cu13.1Zn3.3P29.6, were investigated using synchrotron powder X-ray diffraction. The pressure was applied using a diamond anvil cell. No structural transitions or decomposition were detected in the studied pressure range of 0.1-7 GPa. The calculated bulk modulus for Ba₈Cu13.1Zn3.3P29.6 using a third-order Birch-Murnaghan equation of state is 65(6) GPa at 300 K. This bulk modulus is comparable to the bulk moduli of Ge- and Sn-based clathrates, like A₈Ga16Ge30 (A = Sr, Ba) and Sn19.3Cu4.7P22I₈, but lower than those for the transition metal-containing silicon-based clathrates, Ba₈TxSi46-x, T = Ni, Cu; 3 ≤ x ≤ 5

Synthesis and Characterization of K and Eu Binary Phosphides.

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

Crystal and Electronic Structure and Optical Properties of AE2SiP4 (AE = Sr, Eu, Ba) and Ba4Si3P8

Three new compounds in the AE‐Si‐P (AE = Sr, Eu, Ba) systems are reported. Sr2SiP4 and Eu2SiP4, the first members of their respective ternary systems, are isostructural to previously reported Ba2SiP4 and crystallize in the noncentrosymmetric I42d (no. 122) space group. Ba4Si3P8 crystallizes in the new structure type, in P21/c (no. 14) space group, mP‐120 Pearson symbol, Wyckoff sequence e30. In the crystal structures of Sr2SiP4 and Eu2SiP4 all SiP4 tetrahedral building blocks are connected via formation of P–P bonds forming a three‐dimensional framework. In the crystal structure of Ba4Si3P8, Si‐P tetrahedral chains formed by corner‐sharing, edge‐sharing, and P–P bonds are surrounded by Ba cations. This results in a quasi‐one‐dimensional structure. Electronic structure calculations and UV/Vis measurements suggest that the AE2SiP4 (AE = Sr, Eu, Ba) are direct bandgap semiconductors with bandgaps of ca. 1.4 eV and have potential for thermoelectric applications

High Pressure Properties of a Ba-Cu-Zn-P Clathrate-I.

The high pressure properties of the novel tetrel-free clathrate, Ba₈Cu13.1Zn3.3P29.6, were investigated using synchrotron powder X-ray diffraction. The pressure was applied using a diamond anvil cell. No structural transitions or decomposition were detected in the studied pressure range of 0.1-7 GPa. The calculated bulk modulus for Ba₈Cu13.1Zn3.3P29.6 using a third-order Birch-Murnaghan equation of state is 65(6) GPa at 300 K. This bulk modulus is comparable to the bulk moduli of Ge- and Sn-based clathrates, like A₈Ga16Ge30 (A = Sr, Ba) and Sn19.3Cu4.7P22I₈, but lower than those for the transition metal-containing silicon-based clathrates, Ba₈TxSi46-x, T = Ni, Cu; 3 ≤ x ≤ 5

Zintl Salts Ba2P7X (X = Cl, Br, and I): Synthesis, Crystal, and Electronic Structures

Two barium phosphide halides, Ba2P7Br and Ba2P7I, were synthesized and structurally characterized by single crystal X-ray diffraction. Both compounds crystallize in the monoclinic space group P21/m (No. 11) and are isostructural to Ba2P7Cl. The crystal structures of Ba2P7X (X = Cl, Br, I) feature the presence of heptaphosphanortricyclane P73− clusters along with halogen anions and barium cations. According to the Zintl concept, Ba2P7X compounds are electron-balanced semiconductors. Quantum-chemical calculations together with UV-Visible spectroscopy confirm the title compounds are wide bandgap semiconductors. The bonding in the P73− clusters was analyzed by means of electron localization function. The elemental compositions were confirmed using energy dispersive X-ray spectroscopy

High Pressure Properties of a Ba-Cu-Zn-P Clathrate-I

The high pressure properties of the novel tetrel-free clathrate, Ba8Cu13.1Zn3.3P29.6, were investigated using synchrotron powder X-ray diffraction. The pressure was applied using a diamond anvil cell. No structural transitions or decomposition were detected in the studied pressure range of 0.1–7 GPa. The calculated bulk modulus for Ba8Cu13.1Zn3.3P29.6 using a third-order Birch-Murnaghan equation of state is 65(6) GPa at 300 K. This bulk modulus is comparable to the bulk moduli of Ge- and Sn-based clathrates, like A8Ga16Ge30 (A = Sr, Ba) and Sn19.3Cu4.7P22I8, but lower than those for the transition metal-containing silicon-based clathrates, Ba8TxSi46−x, T = Ni, Cu; 3 ≤ x ≤ 5