T(z) diagram and optical energy gap values of Cu 2(1− z) Mn zIn 2Te 4 alloys

Abstract

The T(z) diagram of the system Cu 2(1− z) Mn z In 2Te 4 was obtained from X-ray powder diffraction and differential thermal analysis measurements. At high temperatures, there is single-phase solid solution across the complete diagram in a disordered defect zinc-blende phase β. This β phase shows a eutectoid reaction at z=0.49 and T=452 °C giving the two tetragonal terminal phases α, CuInTe 2, and γ, MnIn 2Te 4, of space groups I 4 2 d and I 4 2 m, respectively. At lower temperatures, the fields α and γ are separated by a relatively wide two-phase field ( α+ γ) which extends over the range 0.37< z<0.76. Values of room-temperature optical energy gap E o were determined from optical absorption measurements in the ranges of single-phase behaviour, and the form of the E o vs. z data curve is discussed. The form of this T(z) diagram is compared with those of related systems in which the terminal compounds have similar structure but differ in space group.