Mössbauer Spectroscopic Study of FeCl3-doped Polyacetylene

Abstract

Mössbauer spectra of FeCl₃-doped polyacetylenes [CH(FeCl₃)_y]_x (y=0.074, 0.087, and 0.13), which exhibit high electrical conductivities of ≈800, ≈800, and ≈100 S/cm at room temperature, have been measured at the temperatures of 290, 196, 78, and 5 K, respectively. The spectra consist of a superposition of two quadrupole-split doublets, described as doublet (A) and doublet (B), at 290, 196, and 78 K. At 5 K the doublet (A) splits into six lines arising from the magnetic hyperfine interaction, whereas the doublet (B) still remains paramagnetic. The doublet (B) increases remarkably in the Mössbauer absorption with decreasing temperature and is predominant. The values of the isomer shift, the quadrupole splitting, and the internal magnetic field, indicate that the iron compounds corresponding to the doublet (A) and (B) are FeCl₂·nH₂O (n=1 and/or 2) and FeCl₄⁻, respectively. These results established that the mechanism of the FeCl₃-doping process in polyacetylene is as follows: