Composite copper chalcogenide halides: Neutron powder diffraction of CuClCu2TeS3 and electrical properties of CuClCu2TeS3, (CuI)(2)Cu3SbS3, and (CuI)(3)Cu2TeS3

The crystal structure of CuClCu2TeS3 was refined from TOF neutron powder di ffraction data in order to verify the distribution of chlorine and sulfur, It is a novel derivative of the zincblende type with an ordered distributio n both of the cations Cu+ and Te4+ and of the anions Cl- and S2-, The compo und crystallizes in the rhombohedral system, space group R3m (No. 160) with a=7.3502(1) Angstrom, c=10.3873(2) Angstrom, V= 485.99 and Z= 3. The struc ture refinement converged to R-wp=0.039 and R-Bragg = 0.032, From the neutr on data it can be derived that there is no significant disorder of Cl- and S atoms, Impedance spectroscopic measurements in the temperature range 140- 280 degrees C reveal that CuClCu2TeS3 is a semiconductor with an activation energy of 0.75 eV (T< 200 degrees C) and 1.25 eV (Tr 200 degrees C), respe ctively. On the other hand (CuI)(3)Cu2TeS3 and (CuI)(2)Cu3SbS3 exhibit high copper ion conductivity with activation energies of 0.2 and 0.35 eV, respe ctively, but a negligible electronic conduction. (C) 1999 Academic Press.