T(z) Diagram and Optical Energy Gap Values of (AgIn)2(1-z)(MnIn2)zTe4 Alloys

Abstract

The T(z) diagram of the system (AgIn)2(1-z)(MnIn2)zTe4 was obtained from X-ray powder diffraction and differential thermal analysis measurements. At high temperatures, there is a 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 = 0.63 and T = 465°C giving the two tetragonal terminal phases α, AgInTe2, and γ, MnIn2Te4, of space groups I4̄ 2d and I4̄ 2m 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 0.52 < z < 0.78. Values of room-temperature optical energy gap Eo were determined from optical absorption measurements in the ranges of single-phase behavior, and the form of the Eo 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.