ZrB_2粒径对Si_3N_4-ZrB_2陶瓷相组成、显微结构及电阻率的影响

Influence of ZrB_2 Particle Size on Phase Composition,Microsturcture and Electrical Resistivity of Si_3N_4-ZrB_2 Ceramics

以20vol%ZrB_2粗粉和细粉为导电相,以3vol%MgO-2vol%YB_2O_3烧结助剂,通过热压烧结在1500℃制备了Si_3N_4-ZrB_2复相陶瓷,研究了ZrB_2粒径对致密度、相组成、显微结构以及电阻率的影响。结果表明,不依赖于ZrB_2粒径,通过引入MgO-YB_2O_3烧结助剂,均可以获得高致密Si_3N_4-ZrB_2陶瓷。以ZrB_2粗粉为原料时,Si_3N_4-ZrB_2陶瓷包含主要的α-Si_3N_4、β-Si_3N_4和ZrB_2相以及微弱的Yb_4Si_2N_2O_7相,由于ZrB_2晶粒保持孤立状态,样品电阻率较高,为9.5×10~3Ω·m;而以ZrB_2细粉为原料时,其与Si_3N_4发生轻微的高温反应,除了包含主要的α-Si_3N_4、β-Si_3N_4和ZrB_2相及微弱的Yb_4Si_2N_2O_7相之外,Si_3N_4-ZrB_2陶瓷还含有新生成的微弱ZrSi_2和ZrN导电相,由于ZrB_2晶粒保持连通状态,样品电阻率显著降低,仅有6.8Ω·m。

Si_3N_4-ZrB_2 ceramics were fabricated by hot pressing at 1500 ℃,using the coarse and fine20vol% ZrB_2 powders as conductive phase,and 3vol% MgO-2vol% YB_2O_3 as sintering additive. The effect of ZrB_2 particle size on the densification, phase composition, microstructure and electrical resistivity was studied. The result show that dense Si_3N_4-ZrB_2 ceramic could be obtained with the introduction of MgO-YB_2O_3 additives,being independent of ZrB_2 particle size. When coarse ZrB_2 powders were used as raw material,the Si_3N_4-ZrB_2 ceramics contained main α-Si_3N_4,β-Si_3N_4,ZrB_2 phase and weak Yb_4Si_2N_2O_7phase; ZrB_2 grains isolated from each other,the electrical resistivity is about 9. 5 × 10~3Ω·m. However,using fine ZrB_2 powders as raw material,Si_3N_4-ZrB_2 ceramics contained newly weak ZrSi_2 and ZrN conductive phase, in addition to main α-Si_3N_4,β-Si_3N_4,ZrB_2 phase, and weak Yb_4Si_2N_2O_7 phase,the Si_3N_4-ZrB_2 ceramics contained newly weak ZrSi_2 and ZrN conductive phases due to weak reaction of ZrB_2 with Si_3N_4. The electrical resistivity was obviously decreased to 6. 8 Ω·m due to the ZrB_2 grain connection.