Tailoring dielectric properties of PDCs-SiCN with bimodal pore-structure by annealing combined with oxidation

This paper developed a novel strategy, i.e., annealing combined with oxidation to realize high epsilon(r)' (> 7.5) and low tans (< 0.2) in PDC-SiCN. The as-pyrolyzed SiCN prepared by powder consolidation was an amorphous ceramic composed of Si -C-N matrix and free carbon with a bimodal pore-structure. Dielectric properties and pore size distributions can be adjusted by annealing. Oxidation of materials featured an oxide scale on the surface and non-uniform erosion of phases in which additional loss of free carbon occurred. Dielectric properties and their response to oxidation were different under various annealing temperature. When annealing temperature reached 1500 degrees C, sharp rise in epsilon(r)', epsilon(r)'' and tans with increasing temperature happened due to enhanced polarization and electrical conduction. Oxidation at 600 Clowered the Er since depletion of free carbon broke the percolating conducing path. epsilon(r)' maintained at a high level because SiC and most of the heterogeneous interface contributed to epsilon(r)' were preserved.