Titanium diselenide (TiSe₂) also known as titanium(IV) selenide, is an

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemist ...

of titanium and selenium. In this material selenium is viewed as selenide (Se²⁻) which requires that titanium exists as Ti⁴⁺. Titanium diselenide is a member of

metal dichalcogenide : 220px, Cadmium sulfide, a prototypical metal chalcogenide, is used as a yellow pigment. A chalcogenide is a chemical compound consisting of at least one chalcogen anion and at least one more electropositive element. Although all group 16 elements ...

s, compounds that consist of a metal and an element of the chalcogen column within the periodic table. Many exhibit properties of potential value in battery technology, such as

intercalation Intercalation may refer to: * Intercalation (chemistry), insertion of a molecule (or ion) into layered solids such as graphite *Intercalation (timekeeping), insertion of a leap day, week or month into some calendar years to make the calendar foll ...

and electrical conductivity, although most applications focus on the less toxic and lighter disulfides, e.g. TiS₂.

Structure

Within the titanium-selenium system, many stoichiometries have been identified. Titanium diselenide crystallizes with the CdI₂ -type structure, in which the octahedral holes between alternating hexagonal closely packed layer of Se²⁻ layers (that is half of the total number of octahedral holes) are occupied by Ti⁴⁺ centers. The CdI₂ structure is often referred to as a layer structure as the repeating layers of atoms perpendicular to the close packed layer form the sequence Se-Ti-Se^…Se-Ti-Se^…Se-Ti-Se with weak van der Waals interactions between the selenium atoms in adjacent layers. The structure has (6,3)-coordination, being octahedral for the cation and trigonal pyramidal for the anions. The structure type is found commonly for many transition metal

halide In chemistry, a halide (rarely halogenide) is a binary chemical compound, of which one part is a halogen atom and the other part is an element or radical that is less electronegative (or more electropositive) than the halogen, to make a fluor ...

s as well. This layered structure is known to undergo

by alkali metals (M), resulting in the formation of M_xTiSe₂ (x ≤ 1), thereby expanding the weak van der Waals gaps between the 2D layered sheets.

Synthesis

A mixture of titanium and selenium are heated under argon atmosphere to produce crude samples. The crude product is typically purified by

chemical vapor transport In chemistry, a chemical transport reaction describes a process for purification and crystallization of non- volatile solids. The process is also responsible for certain aspects of mineral growth from the effluent of volcanoes. The technique is ...

using iodine as the transport agent.Hagenmuller, P. "Preparative Methods in Solid State Chemistry" :Ti + 2 Se → TiSe₂

References

{{Selenides Selenides Titanium(IV) compounds Transition metal dichalcogenides