T(Z) DIAGRAM AND OPTICAL-ENERGY CAP VALUES OF (AGIN)(2(1-Z))(MNIN2)(Z)TE-4 ALLOYS

The T(z) diagram of the system (AgIn)(2(1-z))(MnIn2)(z)Te-4 was obtain ed from X-ray powder diffraction and differential thermal analysis mea surements. At high temperatures, there is a single-phase solid solutio n across the complete diagram in a disordered defect zinc-blende phase beta. This beta phase shows a eutectoid reaction at z = 0.63 and T = 465 degrees C giving the two tetragonal terminal phases alpha, AgInTe2 , and gamma, MnIn2Te4, of space groups I (4) over bar 2d and 1 (4) ove r bar 2m respectively. At lower temperatures, the fields alpha and gam ma are separated by a relatively wide two-phase field (alpha + gamma) which extends over the range 0.52 < z < 0.78. Values of room-temperatu re optical energy gap E(o) were determined from optical absorption mea surements in the ranges of single-phase behavior, and the form of the E(o) vs z data curve is discussed. The form of this T(z) diagram is co mpared with those of related systems in which the terminal compounds h ave similar structure but differ in space group. (C) 1995 Academic Pre ss, Inc.