METALLIC TEMPERATURE-DEPENDENCE OF RESISTIVITY IN PERCHLORATE DOPED POLYACETYLENE

We have measured the electrical resistivity (rho) and thermoelectric p ower (TEP) of the perchlorate (ClO4-) doped stretch oriented polyacety lene (PA) firm. For the highly conducting samples (sigma(RT) approxima te to 41000 Slcm), the temperature dependence of the four-probe resist ivity shows positive temperature coefficient of resistivity (TCR) from T = 1.5 to 300 K. For the less conducting samples, the four-probe res istivity data show the crossover of TCR with a broad minimum peak at T = T approximate to 200 K. For samples of sigma(RT) greater than or e qual to 20000 S/cm, rho(1.5 K)/rho(300 K) < 1, i.e., the resistivity a t 1.5 K is lower than the room temperature resistivity value. The temp erature dependence of the TEP shows diffusive linear metallic TEP beco ming temperature independent below 40 K. Unlike the others who used Cu (ClO4)(2)for the ClO4- doping, the initial doping material we used is anhydrous Fe(ClO4)(3) which is crucial to obtain positive TCR from T = 1.5 to 300 K. (C) 1998 Elsevier Science S.A. All rights reserved.