• Smuda, M.
• Ströh, J.
• Finzel, Kati
• Khadiev, A.
• Pienack, N.
• Terraschke, H.
• Doert, Thomas
• Hantusch, M.
• Ruck, Michael

Abstract

<p>Intermetallic phases are usually obtained by crystallization from the melt. However, phases containing elements with widely different melting and boiling points, as well as nanoparticles, which provide a high specific surface area, are hardly accessible via such a high-temperature process. The polyol process is one option to circumvent these obstacles by using a solution-based approach at moderate temperatures. In this study, the formation of Bi2Ir nanoparticles in a microwave-assisted polyol process was investigated. Solutions were analyzed using UV-Vis spectroscopy and the reaction was tracked with synchrotron-based in situ powder X-ray diffraction (PXRD). The products were characterized by PXRD and high-resolution transmission electron microscopy. Starting from Bi(NO3)3 and Ir(OAc)3, the new suboxide Bi4Ir2O forms as an intermediate phase at about 160 °C. Its structure was determined by a combination of PXRD and quantum-chemical calculations. Bi4Ir2O decomposes in vacuum at about 250 °C and is reduced to Bi2Ir by hydrogen at 150 °C. At about 240 °C, the polyol process leads to the immediate reduction of the two metal-containing precursors and crystallization of Bi2Ir nanoparticles.</p>

Topics

• nanoparticle
• impedance spectroscopy
• surface
• melt
• powder X-ray diffraction
• Hydrogen
• transmission electron microscopy
• intermetallic
• crystallization
• Ultraviolet–visible spectroscopy