Synthese und Charakterisierung von binären und ternären Übergangsmetallboriden

vorgelegt von Benedikt Florian PetermüllerAbweichender Titel laut Übersetzung des VerfassersKumulative Dissertation aus vier ArtikelnIm Titel sind die Zahlen und Buchstaben 4, 5, 7, 13, 1.3, 2.7, 2, 3-x, 5, 2+x, 2 jeweils tiefgestelltUniversität Innsbruck, Dissertation, 2018OeBB(VLID)294212

High-pressure synthesis of β-Ir4B5 and determination of the compressibility of various iridium borides

"A new iridium boride, beta-Ir4B5, was synthesized under high-pressure/high-temperature conditions of 10.5 GPa and 1500 degrees C in a multianvil press with a Walker-type module. The new modification beta-Ir4B5 crystallizes in a new structure type in the orthorhombic space group Pnma (no. 62) with the lattice parameters a = 10.772(2) angstrom, b = 2.844(1) angstrom, and c = 6.052(2) angstrom 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 B-11. 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 alpha-Ir4B5, beta-Ir4B5, Ir5B4, hexagonal Ir4B3-x and orthorhombic Ir4B3-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.