Electrical Conductivity of SiOCN Ceramics by the Powder-Solution-Composite Technique

SiOCN ceramics have been prepared by the polymer pyrolysis method. The preceramic polymers were synthesized from a polysiloxane cross-linked with two different N-containing compounds: a silazane or a ternary amine. The corresponding SiOCN ceramics were obtained by pyrolysis in nitrogen atmosphere at five different temperatures from 1000 degrees C to 1400 degrees C. The electrical conductivity of the powdered SiOCN ceramic samples was determined by the powder-solution-composite technique. The results show an increase in room temperature AC conductivity of three orders of magnitude, from approximate to 10(-5) (S/cm) to approximate to 10(-2) (S/cm), with increasing pyrolysis temperature from 1000 degrees C to 1400 degrees C. Furthermore, the electrical conductivity of the aminederived SiOCN is three to five times higher than that of the silazane-derived ceramic at each pyrolysis temperature. The combined structural study by Raman spectroscopy and chemical analysis suggests that the increase of electrical conductivity with the pyrolysis temperature is due to the sp(3) -to-sp(2) transition of the amorphous carbon phase. The higher conductivity of the aminederived SiOCN is also discussed considering features like the volume% of the free-carbon phase and its possible N-doping.