Structural study of Cu_2−xSe alloys produced by mechanical alloying

The crystalline structures of the superionic high-temperature copper selenides Cu_2−xSe (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-Cu₂Se 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_1.8Se 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.

Computing details

Figures

(Cu2Se)

Crystal data

Cu2Se	Z = ?
Mr = ?	Cu Kα radiation, λ = 1.5418 Å
Cubic, F23	T = 293 K
a = 5.8164 (3) Å	× × mm
V = ? Å^3

Data collection

Radiation source: sealed X-ray tube	k = ?→?
h = ?→?	l = ?→?

Refinement

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Cu1	0.25	0.25	0.25	0.0*
Cu2	0.5	0.5	0.5	0.0*	.42
Cu3	0.3333	0.3333	0.3333	0.0*	.08
Cu4	0.6667	0.6667	0.6667	0.0*	.08
Se	0	0	0	0.0*

(Cu1.8Se)

Crystal data

Cu1.8Se	Z = ?
Mr = ?	Cu Kα radiation, λ = 1.5418 Å
Cubic, Fm3m	T = 293 K
a = 5.7762 (3) Å	× × mm
V = ? Å^3

Data collection

Radiation source: sealed X-ray tube	k = ?→?
h = ?→?	l = ?→?

Refinement

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Cu1	0.25	0.25	0.25	5.2*	0.8
Cu2	0.3333	0.3333	0.3333	1.7*	.03
Se	0	0	0	3.6*