Quasicrystals discovery

A good, accessible overview of quasicrystals, written only a few years after their discovery, is by Ranganathan (1990) Indian metallurgists played a major part in the early research. Many other published reviews require considerable mathematical sophistication before they can be understood by the reader. 

For the first 15 years after the discovery, quasicrystals were studied purely as a compelling scientific issue. Just recently, applications have begun to appear. 

The discovery of quasicrystals has led to a paradigm change in crystallography, expressed even in a new definition of what is a crystal by... 

The Shechtman s discovery has induced the proper boom in researches dealing with synthetic technologies and investigations of the structure, physical and chemical properties of these remarkable objects, which were named quasicrystals... 

At present, a number of quasi-crystalline alloys with icosahedral, decagonal, and octagonal symmetry are synthesized by different methods. The quasicrystalline form of the solids turned out to be widespread in a great extent. The absence of the translation symmetry and the presence of numerous interstitial sites of the different types in the structure of icosahedral quasicrystals makes some of them interesting objects for hydride chemistry. We cannot wait for any sensational discoveries here, as the general laws of M-H interaction do not depend on matrix structure. However, encouraging results were obtained for icosahedral Ti45Zr38Nii7... 

Since the initial discovery of metastable quasicrystals, many ternary inter-metallic compounds have been produced in the quasicrystalline state, which are thermodynamically stable at room temperature. These have been obtained... 

The other important symmetry-related discovery was the quasicrystals. Both the truncated icosahedral structure of buckminsterfullerene and the regular but nonperiodic network of the quasicrystals are related to fivefold symmetry. In spite of this intimate connection between them at an intellectual level, their stories did not cross. The conceptual linkage between them is provided by Fuller s physical geometry and this is also what relates them to the icosahedral structure of viruses (see, Section 9.5.2 on Icosahedral Packing). 

The actual experimental discovery of quasicrystals was a serendipity, notwithstanding some pertaining predictions [28], It used... 

Figure 1-12) [30], This pattern was extended by Alan Mackay into the third dimension and he even produced a simulated diffraction pattern that showed 10-foldedness (Figure 1-13) [31], It was about the same time that Dan Shechtman was experimenting with metallic phases of various alloys cooled with different speeds and observed 10-foldedness in an actual electron diffraction experiment (Figure 1-14) for the first time. The discovery of quasicrystals has added new perspective to crystallography and the utilization of symmetry considerations. 

Figure 9-64 shows some beautiful representatives of quasicrystals and Figure 9-65 depicts another quasicrystal and a modern sculpture that could be taken as an artistic expression of a quasicrystal although the artist was not aware of the existence of such materials. The artistic appearance of quasi crystals, however, predates their scientific entry by centuries [150], The discovery of such cultural monuments has generated lively discussions even in the general press [151], Concluding, we quote again Mackay [155], who stated that... 

As the first reported quasicrystals were metastable phases at room temperature produced by rapid solidification, they were consequently of poor quality. Stable quasicrystals have since been discovered that have revealed very high strucmral perfection, even comparable to single crystals. This discovery made it possible to apply conventional solidification techniques. The preferred method appears to be system-specific, as it depends on the temperature stability of the quasicrystalline phase. If the quasicrystal is only stable at elevated temperatures, for example, it can decompose into a crystalline phase if the melt is solidified slowly. If the phase is thermodynamically stable down to room temperature, as is the case for Al-Pd-Mn, quasicrystals can be grown with conventional cooling rates (e.g. 10°C/h). 

---