Amorphous material

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In physics and chemistry, amorphous material ( Greek μορφή morphé “shape”, “form” with a prefixed alpha privativum  a-, thus for example “without shape”) is a substance in which the atoms are not ordered, but rather irregular Form patterns and only have short-range order but not long-range order .

In contrast to amorphous materials, regularly structured materials are called crystals .


The classic method to create the amorphous state is the "rapid" cooling of a melt or liquid. The condition for the amorphous state is that the atoms or molecules cannot arrange themselves regularly during cooling, that is, the viscosity must exceed a certain value and crystallization must not occur. The critical cooling rate that is necessary to avoid crystallization depends on the material. Classic glasses such as window glass can also be cooled relatively slowly (e.g. 1 K per minute). Most amorphous metals, on the other hand, require a cooling rate of over 1000 K per second. A related method is vapor deposition onto a cooled substrate. Here, too, the atoms lack the time and flexibility to take on the ordered form.

Another way is production by destroying the crystalline order by means of strong mechanical deformation (e.g. in a ball mill), bombardment by ions or strong radiation.

Not every material can be produced in amorphous form.


Since the atoms have a low packing density, the amorphous substance almost always has a lower density than the same substance in crystalline form. The amorphous state is metastable. When an amorphous substance is heated, it can spontaneously crystallize and thus transform into a more stable state. If there is no crystallization beforehand, there is a direct transition into the liquid phase, without a classic phase transition.

Examples and Applications

Glass is a typical amorphous material. Quartz glass is the amorphous form of silicon dioxide (SiO 2 ). One of its crystalline forms is called quartz . Glass is produced by adding substances, so-called glass converters , which prevent a uniform crystal lattice .

Amorphous metals are manufactured industrially in the form of thin foils using rapid solidification. The main areas of application are magnetic materials , soft magnetic alloys (Fe, Ni, Co) and amorphous soldering foil .

Amorphous silicon is a non-crystalline form of the pure semiconductor silicon and is mainly used for thin-film solar cells .

Obsidian is a natural amorphous material of volcanic origin.

Amorphous thermoplastics (plastics) are for example polystyrene (PS), polyvinyl chloride (PVC) or polycarbonate (PC).

An example from nature is honey . Before filling into jars, the honey is warmed up slightly, which turns it into an amorphous state. Depending on the type and processing, it then crystallizes out within a few days or weeks and forms a crystal lattice.

See also


  • Werner Schatt, Hartmut Worch: Materials Science. Wiley-VCH Verlag, Weinheim 2003, ISBN 3-527-30535-1 .

Web links

Wiktionary: amorphous  - explanations of meanings, word origins, synonyms, translations