Abstract: Si3N4-ZrB2 ceramics were fabricated by hot pressing at 1500 ℃,using the coarse and fine 20vol;ZrB2 powders as conductive phase,and 3vol; MgO-2vol; YB2O3 as sintering additive.The effect of ZrB2 particle size on the densification,phase composition,microstructure and electrical resistivity was studied.The result show that dense Si3N4-ZrB2 ceramic could be obtained with the introduction of MgO-YB2O3 additives,being independent of ZrB2 particle size.When coarse ZrB2 powders were used as raw material,the Si3N4-ZrB2 ceramics contained main α-Si3N4,β-Si3N4,ZrB2 phase and weak Yb4Si2N2O7 phase;ZrB2 grains isolated from each other,the electrical resistivity is about 9.5 × 103 Ω · m.However,using fine ZrB2 powders as raw material,Si3N4-ZrB2 ceramics contained newly weak ZrSi2 and ZrN conductive phase,in addition to main α-Si3N4,β-Si3N4,ZrB2 phase,and weak Yb4Si2N2O7 phase,the Si3N4-ZrB2 ceramics contained newly weak ZrSi2 and ZrN conductive phases due to weak reaction of ZrB2 with Si3 N4.The electrical resistivity was obviously decreased to 6.8 Ω · m due to the ZrB2 grain connection.

Key words: Si3N4-ZrB2 ceramics were fabricated by hot pressing at 1500 ℃,using the coarse and fine 20vol;ZrB2 powders as conductive phase,and 3vol; MgO-2vol; YB2O3 as sintering additive.The effect of ZrB2 particle size on the densification,phase composition,microstructure and electrical resistivity was studied.The result show that dense Si3N4-ZrB2 ceramic could be obtained with the introduction of MgO-YB2O3 additives,being independent of ZrB2 particle size.When coarse ZrB2 powders were used as raw material,the Si3N4-ZrB2 ceramics contained main α-Si3N4,β-Si3N4,ZrB2 phase and weak Yb4Si2N2O7 phase;ZrB2 grains isolated from each other,the electrical resistivity is about 9.5 × 103 Ω · m.However,using fine ZrB2 powders as raw material,Si3N4-ZrB2 ceramics contained newly weak ZrSi2 and ZrN conductive phase,in addition to main α-Si3N4,β-Si3N4,ZrB2 phase,and weak Yb4Si2N2O7 phase,the Si3N4-ZrB2 ceramics contained newly weak ZrSi2 and ZrN conductive phases due to weak reaction of ZrB2 with Si3 N4.The electrical resistivity was obviously decreased to 6.8 Ω · m due to the ZrB2 grain connection.