Phase transitions of the anion radical salts of [(C6H5)3PCH3]1−x+ [(C6H5)3AsCH3]x+ (TCNQ)2− (0 ≤ x ≤ 1) as studied by the electrical conductivity measurements

Abstract

The phase transitions of the anion radical salts containing the mixed cations represented by $\mathrm{[(}{\mathrm{C}}_6{\mathrm{H}}_5{)}_3{\mathrm{PCH}}_3{]}_{\text{1−}}^{\mathrm{x;+}}\mathrm{\hspace{0.17em}[(}{\mathrm{C}}_6{\mathrm{H}}_5{)}_3{\mathrm{AsCH}}_3{]}_x^{+}\mathrm{\hspace{0.17em}(}\mathrm{TCNQ}{)}_2^{-}\text{,\hspace{0.17em}(0 ≤ x ≤ 1)}$ , were investigated by measuring the electrical conductivity and its variation with the temperature. All the salts except for that with x = 1.00 were found to show a sharp discontinuity in the temperature dependence of the electrical conductivity. At the temperature where the anomaly occurred, the electrical conductivity increased abruptly in the higher temperature range. The transition temperature, $T_c,$ and the magnitude of the discontinuity of the electrical conductivity at $T_c,$ were determined as a function of the composition parameter. These experimental results were useful for investigating the mechanism of the phase transitions of these anion radical salts.