Fabrication of Si3N4 ceramics substrates with high thermal conductivity by tape casting and gas pressure sintering

In this paper, high thermal conductivity Si 3 N 4 ceramics were successfully fabricated through exploring and optimizing the tape casting process. The impact of various organic additives on the rheological characteristics of Si 3 N 4 slurry was explored, and the pore size distribution and microstructure of the green tapes at different solid loadings were investigated, as well as the microstructure of Si 3 N 4 ceramics. Green tapes with a narrow pore size distribution, a small average pore size, and a high density of 1.88 g cm −3 were prepared by the investigation and optimization of the Si 3 N 4 slurry formulation. After gas pressure sintering, Si 3 N 4 ceramics with a density of 3.23 g cm −3 , dimensions of 78 mm × 78 mm, and a thickness of 0.55 mm were obtained. The microstructure of the Si 3 N 4 ceramics showed a bimodal distribution and a low content of glassy phases. The thermal conductivity of the Si 3 N 4 ceramics was 100.5 W m −1 K −1 , the flexural strength was 735 ± 24 MPa, and the fracture toughness was 7.17 MPa m 1/2 .