T(Z) DIAGRAM AND OPTICAL-ENERGY GAP VALUES OF CU-2(1-Z)MNZIN2TE4 ALLOYS

The T(z) diagram of the system Cu-2((1-z))MnzIn2Te4 was obtained from X-ray powder diffraction and differential thermal analysis measurement s. At high temperatures, there is single-phase solid solution across t he complete diagram in a disordered defect zinc-blende phase beta. Thi s beta phase shows a eutectoid reaction at z=0.49 and T=452 degrees C giving the two tetragonal terminal phases alpha, CuInTe2, and gamma, M nIn2Te4, of space groups 1 $($) over bar$$ 42d and 1 $($) over bar$$ 4 2m, respectively. At lower temperatures, the fields alpha and gamma ar e separated by a relatively wide two-phase field (alpha+gamma) which e xtends over the range 0.37<z<0.76. Values of room-temperature optical energy gap E(0) were determined from optical absorption measurements i n the ranges of single-phase behaviour, and the form, of the E(0) vs. z data curve is discussed. The form of this T(z) diagram is compared w ith those of related systems in which the terminal compounds have simi lar structure but differ in space group.