烧结助剂La_2O_3含量对热压烧结制备Si_3N_4-AlN复相陶瓷性能的影响

Effect of Sintering Additive La_2O_3 Content on Properties of Si_3N_4-AlN Composite Ceramics Prepared by Hot-Pressing Sintering

以Si3N4和AlN为原料,La2O3为烧结助剂,在氮气气氛和1 800℃、30MPa压力下热压烧结保温1 h制备出了Si3N4-AlN复相陶瓷,研究了La2O3含量对复相陶瓷烧结性能、抗弯强度、热导率及介电损耗的影响。结果表明:随La2O3含量的增加,复相陶瓷的孔隙率先减小然后趋于稳定,Si3N4由α相向β相逐渐转变完全,且含镧黄长石晶界相逐渐增多;随La2O3含量的增加,复相陶瓷的抗弯强度逐渐减小,介电损耗先减小后增大,热导率则先增大后减小;在La2O3含量为4%时,抗弯强度达到最大值为574 MPa;在La2O3含量为6%时,介电损耗最低,同时热导率最大,分别为4.55×10-3和11.7W.m-1.K-1。

Si3N4-AlN composite ceramics were prepared by hot-pressing sintering at 1 800 ℃ under 30 MPa for 1 h in nitrogen atmosphere with AlN and Si3N4 as raw materials and La2O3 as sintering additive.The effect of La2O3 content on sintering performance,bending strength,thermal conductivity and dielectric loss of the composite ceramies was investigated.The results show that with the increase of La2O3 content,the porosity of the ceramics decreased first and then reached a fixed value,the phase transformation Si3N4 from α to β was gradually completed and more lanthanum-melilites were found in the grain boundaries.With the increase of La2O3 content,bending strength of the composites decreased gradually,dielectric loss decreased first and then increased,while the thermal conductivity increased first and then decreased.When the La2O3 content was 4% the bending strength reached maximum 574 MPa.The lowest dielectric loss of 4.55×10-3 and highest thermal conductivity of 11.7 W·m-1·K-1 were obtained at a La2O3 content of 6%.