关键词: 氮化硅陶瓷, Y₂O₃-MgO烧结助剂, 凝胶流延成型, Isobam, 两步烧结

Abstract: To address the problem of dense sintering difficulty of covalent bonded silicon nitride materials,Si tape-casting slices were prepared by gel tape-casting using the Isobam (Isobutylene-anhydride maleic) gel system and Si powder as raw materials,extra adding different amounts of sintering aid Y₂O₃-MgO (Y₂O₃ to MgO mole ratio of 4∶3,4%,6%,8% and 10%,by mass).Then they were treated by the two-step firing method,firing at 1 400 ℃ for 2 h and 1 750 ℃ for 2 h in the nitrogen atmosphere to prepare Si₃N₄ ceramic substrate specimens.The effect of the Y₂O₃-MgO addition on the properties of the Si₃N₄ ceramic substrates was investigated.The results show that adding Y₂O₃-MgO can promote the phase transition from α-Si₃N₄ to β-Si₃N₄ in the sintered specimens.With the increasing Y₂O₃-MgO addition from 4% to 8%,more liquid phases are generated during sintering,which promotes the liquid phase mass transfer and leads to the increased number and growth of long columnar β-Si₃N₄ grains,and the densification,hardness,fracture toughness,flexural strength,and thermal conductivity of the specimens increase.However,when the Y₂O₃-MgO addition is 10%,due to the abnormal growth of β-Si₃N₄ grains,all the properties of the specimens decrease.The silicon nitride specimen with 8% Y₂O₃-MgO performs the best comprehensive performance.

Key words: Si₃N₄ ceramics, Y₂O₃-MgO sintering aid, gel tape-casting, Isobam, two-step firing