Ionic conductivity of Ag₃AsS₃ and Ag₃AsSe₃.

Abstract

The conductivities of synthetic Ag₃AsS₃ and Ag₃AsSe₃ have been measured as a function of temperature and frequency by the complex impedance method. Their impedance plots exhibited the characteristic semicircles which were attributed to ionic conduction behaviors in the bulk and the grain boundary. The transport number of charge carrying species in Ag₃AsS₃ was determined by the Tubandt method. The electronic contribution to the total conductivity of Ag₃AsS₃ was negligible small at room temperature; less than 1%. The logσT versus 1/T plot of Ag₃AsS₃ had a kink of the slope near about 375 K. The activation energies below and above 375 K are evaluated as 0.23 and 0.35 eV, respectively. Ag₃AsSe₃, measured only below about 330 K, gave an activation energy of 0.24 eV. The magnitude of the conductivity of Ag₃AsSe₃ is almost ten times larger than that of Ag₃AsS₃ below 375 K. The conductivities of Ag₃AsS₃, 1.5×10⁻³ S/cm at 427 K, and of Ag₃AsSe₃, 1.6×10⁻³ S/cm at 331 K, are sufficient magnitudes as superionic conductors.