Interstitial compound

Red = atoms of element 'B'

Referred to for a solid solution, and interstitial compound or intercalation compound, is a chemical, non-stoichiometric crystalline compound composed of at least two elements.

This type of connection is usually found between metal and non- metal, with the much smaller non-metal atoms ( impurities, interstitials ) interstitial spaces or gaps in the crystal lattice of the metal occupy ( host element, base element). Intercalation compounds often have metallic properties. Important representatives include iron-carbon, tungsten carbide (WC), or Ti2H Fe2N.

In a solid solution whatsoever, lattice distortions, which expand the crystal lattice, as additional atoms to be incorporated into the lattice. To enable this connection, the atomic diameter of the foreign atom may be only about 41 % of the atomic diameter of the host atom. In addition, the storage capacity is greatly limited due to the lattice distortion and the associated stresses. It is, for example, the compound of iron and carbon, depending on the temperature of 0.10% ( δ - mixed crystal ), 2.06 % ( γ - solid solution ) or 0.02% ( α - solid solution ). This means that e.g. in an α - solid solution than 0.2 % of carbon ( at 723 ° C) to 0.02 % may be achieved ( at room temperature).