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

摘要： 针对共价键氮化硅材料难实现致密烧结的问题,以Isobam(异丁烯马来酸酐共聚物)为凝胶体系,Si粉为原料,分别添加不同量的烧结助剂Y₂O₃-MgO(Y₂O₃和MgO的物质的量比为4∶3,外加质量分数分别为4%、6%、8%和10%),通过凝胶流延成型制备了Si流延片,在1 400 ℃氮气气氛下保温2 h后,升温至1 750 ℃保温2 h两步烧结制备了Si₃N₄陶瓷基板试样。探究了烧结助剂外加量对氮化硅陶瓷基板性能的影响。结果表明:添加Y₂O₃-MgO烧结助剂可促进烧结后试样α-Si₃N₄向β-Si₃N₄的转变;随着Y₂O₃-MgO烧结助剂外加量(w)从4%增至8%,烧结过程中生成了更多的液相,促进了液相传质,导致长柱状β-Si₃N₄晶粒增多和生长,试样的致密度、硬度、断裂韧性、抗弯强度、热导率随着烧结助剂外加量的增加而增大。但当烧结助剂外加量(w)为10%时,由于β-Si₃N₄晶粒的异常长大,试样的各项性能均下降。当烧结助剂外加量为8%(w)时,氮化硅试样的综合性能最好。

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