Rapid preparation of Si3N4 ceramics with high thermal conductivity and low dielectric loss by fast hot-pressing (FHP) sintering

A series of Si3N4 3 N 4 ceramics with MgO and Y2O3 2 O 3 as sintering additives were successfully prepared by fast hot- pressing (FHP) sintering at the sintering temperature of 1700 degrees C, with the hold time of only 10 min and the whole sintering process of 36 min. The sintering behavior, densification process, microstructure, crystalline phase composition, bond composition, thermal conductivity and dielectric properties were systematically investigated. FHP reduces the sintering temperature and sintering time of Si3N4 3 N 4 ceramic compared to traditional solid-state method. The results of a series of tests have shown that the densification of Si3N4 3 N 4 ceramics and the phase transition from alpha-Si3N4 3 N 4 to beta-Si3N4 3 N 4 can be facilitated by appropriate levels of additives, resulting in a dense, homogeneous and non-porous microstructure. Additionally, based on test results in this work, Si3N4 3 N 4-4 wt.% Y2O3 2 O 3-2 wt.% MgO exhibit the highest thermal conductivity of 78.16 W/mK, the dielectric constant of 8.50 and the dielectric loss of 5.52 x 10-4.-4 . The Si3N4 3 N 4 ceramics investigated in this work exhibit excellent properties for use of power semiconductor device packages, microwave devices, and power electronics. And also demonstrate the potential of FHP in laying the foundation for the further preparation of higher performance Si3N4 3 N 4 ceramics.