Metallic temperature dependence of resistivity in perchlorate doped polyacetylene

We have measured the electrical resistivity (rho) and thermoelectric power (TEP) of the perchlorate (ClO4-) doped stretch oriented polyacetylene (PA) firm. For the highly conducting samples (sigma(RT) approximate to 41000 Slcm), the temperature dependence of the four-probe resistivity shows positive temperature coefficient of resistivity (TCR) from T = 1.5 to 300 K. For the less conducting samples, the four-probe resistivity 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 equal to 20000 S/cm, rho(1.5 K)/rho(300 K) < 1, i.e., the resistivity at 1.5 K is lower than the room temperature resistivity value. The temperature dependence of the TEP shows diffusive linear metallic TEP becoming 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.