Structural study of Cu2−x Se alloys produced by mechanical alloying

The crystalline structures of the superionic high-temperature copper selenides Cu 2− x Se (0 < x < 0.25) produced using mechanical alloying were investigated using X-ray diffraction (XRD). The measured XRD patterns showed the presence of peaks corresponding to the crystalline superionic high-temperature α-Cu 2 Se phase in the as-milled sample, and its structural data were determined by means of a Rietveld refinement procedure. After heat treatment in argon at 473 K for 90 h, this phase transforms to the superionic high-temperature α-Cu 1.8 Se phase, whose structural data were also determined by Rietveld refinement. In this phase, a very low occupation of the trigonal 32( f ) sites (∼ 3%) by Cu ions is found. In order to explain the evolution of the phases in the samples, two possible mechanisms are suggested: (i) the high mobility of Cu ions in superionic phases and (ii) the important diffusive processes in the interfacial component of samples produced by mechanical alloying.