Journal of the American Ceramic Society, Vol.103, No.4, 2630-2642, 2020
Semiconductor-conductor transition of pristine polymer-derived ceramics SiC pyrolyzed at temperature range from 1200 degrees C to 1800 degrees C
This paper studies the effect of pyrolysis temperature on the semiconductor-conductor transition of pristine polymer-derived ceramic silicon carbide (PDC SiC). A comprehensive study of microstructural evolution and conduction mechanism of PDC SiC pyrolyzed at the temperature range of 1200 degrees C-1800 degrees C is presented. At relatively lower pyrolysis temperatures (1200 degrees C-1600 degrees C), the carbon phase goes through a microstructural evolution from amorphous carbon to nanocrystalline carbon. The PDC SiC samples behave as a semiconductor and the electron transport is governed by the band tail hopping (BTH) mechanism in low pyrolysis temperature (1300 degrees C); by a mixed mechanism driven by band tail hopping and tunneling at intermediate temperature (1500 degrees C). At higher pyrolysis temperatures (1700 degrees C-1800 degrees C), a percolative network of continuous turbostratic carbon is formed up along the grain boundary of the crystallized SiC. The samples demonstrate metal-like conductive response and their resistivity increases monotonically with the increasing measuring temperature.