Temperature dependent AC electric conduction of polymer-derived SiAlCN ceramics

摘要

The polymer-derived SiAlCN ceramic was synthesized by thermal decomposition of an Al-containing polymeric precursor at 1000 degrees C. The impedance spectra of the ceramic were measured in the frequency range of 20 Hz to 20 MHz at temperatures up to 500 degrees C. The results show that the conductivity of the material increases gradually with increasing testing temperature and frequency, which behaves a typical NTC characteristic. The overlapping of normalized peaks/lines corresponding to electric modulus/electric conductivity indicates that the material follows an identical conductive mechanism regardless of frequency in the temperature range. The results also reveal that the conductivity followed T-1/4 dependence, corresponding to a 3D hopping process. Analysis of the relationship between sigma(0) vs T-0 reveals that the conductive mechanism is band-tail hopping rather than variable range hopping.