Microstructure and properties of porous silicon nitride ceramics prepared by gel-casting and gas pressure sintering

• Published in: Materials in engineering Vol. 44; pp. 114 - 118
• Main Authors: Zou, Chunrong, Zhang, Changrui, Li, Bin, Wang, Siqing, Cao, Feng
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.02.2013
• Subjects: Anisotropy; Ceramics; Elongation; Flexural strength; Gas pressure; Grains; Microstructure; Nitrides; Porosity; Sintering (powder metallurgy)
• ISSN: 0261-3069
• DOI: 10.1016/j.matdes.2012.07.056

► Gel-casting and GPS is an effective way to prepare porous Si3N4 ceramics. ► Porosity and microstructure are largely dependent on the solid loadings. ► Porous Si3N4 ceramics have desirable mechanical properties. ► Porous Si3N4 ceramics have suitable dielectric properties. Wave-transparent porous Si3N4 ceramics were prepared by gel-casting and gas pressure sintering, and the effects of solid loading on microstructure, mechanical and dielectric properties were investigated. Microstructures with interlocked elongated β-Si3N4 grains and uniformly distributed pores were observed, while both the β-Si3N4 phase content and grain aspect ratio reduced as the solid loading increased due to the restrained anisotropic growth of β-Si3N4 grains. As the solid loading increased from 30 to 45vol.%, the porosity of ceramics declined from 57.6% to 36.4%. The flexural strength increased linearly from 108.3 to 235.1MPa, and the dielectric constant and loss tangent of ceramics increased from 2.63 and 2.85×10−3 to 3.68 and 3.56×10−3 (10GHz), respectively.