Quality assessment of Al–Cu–Fe quasicrystals: methods and results

Evaluation of the quality of quasicrystals of the Al–Cu–Fe system is a multifaceted task that requires consideration of many factors, from structural perfection to microscopic defects. There is a whole range of methods that allow characterizing quasicrystalline materials, but an integrated indicator that takes into account key parameters and is suitable for comparative evaluation of various samples is still the subject of active research.

One of the most important aspects is determining the degree of order in the quasi-crystalline structure. X-ray diffraction methods allow us to estimate the width and intensity of diffraction peaks, which reflect the presence and nature of defects, such as phase inhomogeneities, dislocations and point defects. Narrow and intense peaks indicate a high degree of order and a minimum number of defects. However, interpretation of X-ray diffraction results requires caution, since even minor impurities or stresses can have a significant effect on the diffraction pattern.

Study of quasicrystals: from structure to electrical properties

Quasicrystals of icosahedral structure, characterized by low thermal conductivity in combination with moderate electrical conductivity and a fairly high value of the thermoelectric power factor, are of interest for use in thermoelectric generators. The paper presents theoretical justifications for explaining the electrical properties and thermoelectric force inherent in two representatives of the Al–Cu–Fe quasicrystalline family (i-Al62Cu25.5Fe12.5 and i-Al63Cu25Fe12). It should be noted that their energy conversion efficiency values ​​still remain low when compared with the most common thermoelectric materials.

Another important parameter is the stoichiometric composition. Deviations from the optimal ratio of Al, Cu and Fe can lead to the formation of secondary phases and disruption of the quasi-crystalline structure. Atomic emission spectrometry (AES) and X-ray photoelectron spectroscopy (XPS) methods allow for precise determination of the elemental composition and assessment of the degree of homogeneity of the material.

Microscopic techniques such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM) allow the microstructure to be visualized and the presence of defects, grain boundaries, and other inhomogeneities to be detected. Analysis of images obtained using these techniques can provide valuable information about the quality of quasicrystals and their suitability for various applications.

Author:

A Bilušić, D Pavuna, A Smontara

Institute:
Institute of Physics, P.O. Box 304, HR-10001 Zagreb, Croatia

Institute of Applied Physics, Federal Polytechnic School, CH-1015 Lausanne, Switzerland