MILLIMETER-WAVE EFFECT ON SINTERING OF SILICON NITRIDES BY 28GHz MILLIMETER-WAVE RADIATION

摘要

Si_3N_4 powders containing Yb_2O_3-Al_2O_3 aids were heated and sintered by 28GHz millimeter-wave (mm-wave) radiation. The mm-wave heating efficiently decreased sintering temperature by about 200 to 400℃ compared with that of conventional gas pressurized sintering, and the temperature decrease was strongly affected by the content of Yb_2O_3-Al_2O_3 aids. Especially the specimen containing 6.4wt%Yb_2O_3-1.6wt%Al_2O_3 sintering aids, which was the eutectic composition of Yb_2O_3-Al_2O_3, could be densified at 1600℃ by the mm-wave heating. This temperature was about 400℃ lower than that of the conventional heating. The mechanical properties of the specimen indicated a value around 900MPa in 3-point bending test and 6 to 7MPa m~(1/2) in indentation fracture method, while conventionally sintered samples gave a value of 540MPa and below 6 MPa· m~(1/2) respectively. These properties of mm-wave sintered specimen were verified to come from well-bonded interface between the Si_3N_4 grain and the residual glass originated in Yb_2O_3-Al_2O_3 aids.