Composite Copper Chalcogenide Halides: Neutron Powder Diffraction of CuClCu2TeS3 and Electrical Properties of CuClCu2TeS3, (CuI)2Cu3SbS3, and (CuI)3Cu2TeS3

The crystal structure of CuClCu2TeS3 was refined from TOF neutron powder diffraction data in order to verify the distribution of chlorine and sulfur. It is a novel derivative of the zincblende type with an ordered distribution both of the cations Cu+ and Te4+ and of the anions Cl- and S2-. The compound crystallizes in the rhombohedral system, space group R3m (No. 160) with a=7.3502(1) ?, c=10.3873(2) ?, V=485.99 ?3, and Z=3. The structure refinement converged to Rwp=0.039 and RBragg= 0.032. From the neutron 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°C reveal that CuClCu2TeS3 is a semiconductor with an activation energy of 0.75 eV (T<200°C) and 1.25 eV (T>200°C), respectively. On the other hand (CuI)3Cu2TeS3 and (CuI)2Cu3SbS3 exhibit high copper ion conductivity with activation energies of 0.2 and 0.35 eV, respectively, but a negligible electronic conduction.