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

In this paper, high thermal conductivity Si3N4 ceramics were successfully fabricated through exploring and optimizing the tape casting process. The impact of various organic additives on the rheological characteristics of Si3N4 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 Si3N4 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 Si3N4 slurry formulation. After gas pressure sintering, Si3N4 ceramics with a density of 3.23 g cm(-3), dimensions of 78 mm x 78 mm, and a thickness of 0.55 mm were obtained. The microstructure of the Si3N4 ceramics showed a bimodal distribution and a low content of glassy phases. The thermal conductivity of the Si3N4 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).