Extension of the two-phase field in the system 2(ZnS)x(CuInS2)1−x and structural relationship between the tetragonal and cubic phase

The two-phase field in the system 2(ZnS)x(CuInS2)1−x, where cubic and tetragonal mixed crystals coexist, covers at room temperature the compositional range 0.10⩽x⩽0.41. For 0⩽x<0.10 alloys with tetragonal structure only exist. Above 41 mol% 2(ZnS) exclusively solid solutions of 2(ZnS)x(CuInS2)1−x having cubic structure without any cation ordering are stable. Equilibrium and kinetic experiments enabled to check the effect of temperature and cooling rate on the chemical compositions of both phases and on the growth kinetics of domains. The compositions of the different phases and their structural relationship were measured by EDX in a transmission electron microscope (TEM) and by selected area diffraction, TEM and HRTEM. After nucleation of the discus-shaped domains, their growth obeys t1/2, i.e. it is controlled by diffusion. The short extension of the domains lies always parallel to their tetragonal c-axis. They are simultaneously arranged on the (1 0 0),(0 1 0) and (0 0 1) planes within the cubic matrix. While slow cooling with < 2 K/h approximates the equilibrium at room temperature, long-time annealing experiments at higher temperatures followed by rapid quenching enabled to determine the chemical compositions at the annealing temperature. If the samples are far away from the equilibrium state within both phases cation ordering like the stannite-type occurs. The more both phases approach the equilibrium the more they become disordered.