High-Pressure Synthesis of ?-Ir₄B₅ and Determination of the Compressibility of Various Iridium Borides.

ABSTRACT: A new iridium boride, ?-Ir₄B₅, was synthesized under high-pressure/high-temperature conditions of 10.5 GPa and 1500 °C in a multianvil press with a Walker-type module. The new modification ?-Ir₄B₅ crystallizes in a new structure type in the orthorhombic space group Pnma (no. 62) with the lattice parameters a = 10.772(2) Å, b = 2.844(1) Å, and c = 6.052(2) Å with R1 = 0.0286, wR2 = 0.0642 (all data), and Z = 2. The structure was determined by single-crystal X-ray and neutron powder diffraction on samples enriched in ¹¹B. The compound is built up by an alternating stacking of boron and iridium layers with the sequence ABA'B'. Additionally, microcalorimetry, hardness, and compressibility measurements of the binary iridium borides ?-Ir₄B₅, ?-Ir₄B₅, Ir₅B₄, hexagonal Ir₄B_{3- x} and orthorhombic Ir₄B_{3- x} were carried out and theoretical investigations based on density function theory (DFT) were employed to complement a comprehensive evaluation of structure-property relations. The incorporation of boron into the structures does not enhance the compressibility but leads to a significant reduction of the bulk moduli and elastic constants in comparison to elemental iridium.

SUBMITTER: Petermuller B 

PROVIDER: S-EPMC6106047 | biostudies-literature | 2018 Aug

REPOSITORIES: biostudies-literature