Influence of Phase Formation on Dielectric Properties of Si 3 N 4 Ceramics

The influence of phase formation on the dielectric properties of silicon nitride (Si 3 N 4 ) ceramics, which were produced by pressureless sintering with additives in MgO–Al 2 O 3 –SiO 2 system, was investigated. It seems that the difference in the dielectric properties of Si 3 N 4 ceramics sintered at different temperatures was mainly due to the difference of the relative content of α‐Si 3 N 4 , β‐Si 3 N 4 , and the intermediate product (Si 2 N 2 O) in the samples. Compared with α‐Si 3 N 4 and Si 2 N 2 O, β‐Si 3 N 4 is believed to be a major factor influencing the dielectric constant. The high‐dielectric constant of β‐Si 3 N 4 could be attributed to the ionic relaxation polarization.