以硅粉(Si)和炭黑(C)为原料、聚四氟乙烯(PTFE)为助燃剂、铝粉(Al)为掺杂源,在低压氮气气氛中通过燃烧合成的方法制备出Al掺杂β-SiC粉体.用XRD、SEM和EDS对其进行了表征,同时在频率8.2～12.4 GHz范围内对其进行介电常数的测试.结果表明未掺杂Al时生成富碳β-SiC粉体;当掺杂Al时并未生成AlN-SiC固溶体,而是Al原子进入到碳化硅晶格中占据硅的位置形成了Al/SiC固溶体,引起β-SiC晶格常数的逐渐增大.当Al掺杂含量为5 mol%时晶粒最小,同时出现了Al_2O_3杂质相,但是其介电常数实部和介电损耗达到最大值,同时对Al对β-SiC介电损耗的影响进行了讨论.
The Al-doped β-SiC powders were obtained by combustion synthesis under low nitrogen pressure (0.1 MPa) using silicon and carbon black as raw materials, polytetrafluoroethylene (PTFE) as additive and aluminum (Al) as doping source. The crystallites of combustion products were characterized by X-ray diffractometry (XRD), scanning electron microscope (SEM) and energy dispersive spectra (EDS). The microwave dielectric properties of prepared powders were measured in the frequency range of 8.2～12.4 GHz. The results indicate when the Al content is 0 the prepared powder is C-rich β-SiC powder. However, when the Al content is not 0 no AlN-SiC solid solutions are generated. The Al atoms enter the β-SiC lattice, substituting for the Si atoms and leading to the increase of lattice constant of β-SiC. When the Al content is 5mol%, the average size of particle is minimum and the dielectric real and imaginary part reach maximum. The effect of Al doping on dielectric loss of β-SiC was discussed.
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