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Register a new userTemperature dependent charge transport mechanisms in carbon sphere/polymer composites
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Added by
Natalya A. Zimbovskaya
Publication date
2017
fields
Physics
and research's language is
English
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Carbon spheres (CS) with diameters in the range $2 - 10 mu m$ were prepared via hydrolysis of a sucrose solution at $200^o C,$ and later annealed in $N_2$ at $800^o C.$ The spheres were highly conducting but difficult to process into thin films or pressed pellets. In our previous work, composite samples of CS and the insulating polymer polyethylene oxide (PEO) were prepared and their charge transport was analyzed in the temperature range $ 80 K < T < 300 K. $ Here, we analyze charge transport in CS coated with a thin polyaniline (PANi) film doped with hydrochloric acid (HCl), in the same temperature range. The goal is to study charge transport in the CS using a conducting polymer (PANi) as a binder and compare with that occurring at CS/PEO. A conductivity maxima was observed in the CS/PEO composite but was absent in CS/PANi. Our data analysis shows that variable range hopping of electrons between polymeric chains in PANi-filled gaps between CS takes on a predominant part in transport through CS/PANi composites, whereas in CS/PEO composites, electrons travel through gaps between CS solely by means of direct tunneling. This difference in transport mechanisms results in different temperature dependences of the conductivity.
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A set of uniform carbon microspheres (CS) whose diameters have the order of $ 0.125 mu m$ to $10 mu m $ was prepared from aqueous sucrose solution by means of hydrothermal carbonization of sugar molecules. A pressed pellet was composed by mixing CSs with polyethylene oxide (PEO). Electrical characterization of the pellet was carried out showing Ohmic current-voltage characteristics and temperature-dependent conductivity in the range $ 80K < T < 300K.$ The conductivity reached a maximum value of $ 0.245 S/cm $ at $ 258K. $ The dependence of conductivity on temperature was theoretically analyzed to determine predominating mechanisms of electron transport. It was shown that thermally-induced electron tunneling between adjacent spheres may take on an important part in the electron transport through the CS/PEO composites.
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