Additives for Low-Temperature Sintering of AlN Ceramics with High Thermal Conductivity and High Strength

摘要

Thermodynamical consideration indicates that Li_2O, Y_2O_3 and CaO are effective sintering aids for AlN sintering. Commercially available AlN powders were pressureless-sintered with concurrent additions of Y_2O_3-CaO, Li_2O-Y_2O_3-CaO and LiYO_2 (Y_2O_3 • Li_2O)-CaO. Doping with Li_2O and LiYO_2 caused densification of AlN ceramics at a processing temperature of 1600 ℃. This is due to reduction of liquidus temperature in the Y_2O_3-CaO-Al_2O_3-AlN system and to improvement of wettability between liquid and AlN. Among the specimens tested, AlN specimens with LiYO_2 and CaO addition obtAlNed at 1600 ℃ for 6 h indicated a high thermal conductivity of 172 Wm~(-1)K~(-1) and a high strength of 450 MPa.