Copper substitutions in synthetic miargyrite α-AgSbS2 mineral: synthesis, characterization and dielectrical properties

Abstract

The nominal compositions Ag0.8Cu0.2SbS2 and Ag0.7Cu0.3SbS2 have been synthesized by conventional ceramic solid-state reaction at high temperature. X-ray diffraction (XRD) and scanning electron microscopy chemical analysis (SEM-EDAX) revealed single phases, isostructural to the natural miargyrite a- AgSbS2 mineral. Examination of the lattice parameters shows a decrease in the cell volume with increasing copper substitutions. The Raman analysis displays absorptions which may be assigned to the SbeS stretching vibrations of the SbS3 pyramids. The impedance-frequency analysis showed grain boundary and electrode interface contributions in non-Debye type relaxation, following Jonscher’s universal power law. The giant permittivity response is attributed to extrinsic effects without evidence of a ferroelectric transition. Summerfield scaling, leading to the superposition of impedance analysis, implies that the relaxation is thermally activated, without introducing more than one underlying transport mechanism.