Composition, structure, and dielectric properties of SiC-AlN ceramic materials

We have studied the structure, relative dielectric permittivity (?), and dielectric loss tangent (tan??) of SiC-AlN ceramic materials. The results demonstrate that both ? and tan?? are anomalously high in the composition range 30?C50 wt % AlN at low frequencies (0.1 kHz). We show that the increase in ? may be due to a barrier effect on silicon carbide and aluminum nitride grain boundaries and to migration polarization.