Aluminium telluride

Properties

Aluminium telluride is a very air-sensitive dark grey to black solid. It has a band gap of 2.4 eV. The compound decomposes in humid air.

In its pure form, it occurs in at least two phases. The orange-red low-temperature (α) modification transforms into the yellow high-temperature (β) form at 720 °C (993 K; 1,328 °F). The conversion from β- to α-Al₂Te₃, which is associated with such a small enthalpy change that it cannot be observed with differential thermal analysis, takes place after prolonged annealing just below the conversion point. The α form crystallizes in the monoclinic crystal system with the lattice constants a = 13.885 Å, b = 7.189 Å, c = 4.246 Å, p = 90.21° and an additional superstructure. The β form has a monoclinic crystal structure with space group P2₁/c and the lattice constants a = 7.181(1) Å, b = 12.848(3) Å, c = 14.167(3) Å, and b= 90.04(2)°. This form represents a separate structure type. The tellurium atoms form a hexagonal dense packing parallel to the (001) plane; one-third of the tetrahedral vacancies are occupied by aluminium atoms, whereby the tetrahedral vacancies are occupied in such a way that a layered structure is formed. Some sources also report another form of the defect wurtzite type.

Uses

Aluminium telluride is used in the semiconductor industry. It can also be used to produce hydrogen telluride by reacting with hydrogen chloride.

Al₂Te₃ + 6 HCl → 3 H₂Te + 2 AlCl₃