七种新的SiC六方多型体

本文提出了用X射线劳埃法鉴定SiC六方多型体类型的方法。在详细地研究了xH类型与基本类型6H,15R和4H的倒易阵点间相互配置关系的基础上,推导出了这些具体关系,这种关系对于xH—6H来说仅有十二种,对于xH—15R仅有三十种,对于xH—4H仅有八种。上述的点间关系表和推求xH类型单位晶胞密堆积层数的公式同样可以普遍适用于以其他X射线照相法鉴定SiC六方多型体类型的工作中。用本文所提出的方法研究了许多实验室升华法制备的SiC单晶体以及部分工业SiC晶体。发现了七种六方SiC新多型体141H,80H,58H,55H,15H,9H和7H。新类型的定间羣为C_3v¹(C3m),六方晶胞c轴参数分别为:355.26?,201.57?,146.14?,138.58?,37.794?,22.676?和17.637?。

SEVEN NEW HEXAGONAL POLYTYPES OF SILICON CARBIDE

A method for determining the hexagonal polytypes of silicon carbide using the Laue pattern is described. By the detailed studies on reciprocal lattice points of various hexagonal types xH of silicon carbide which are coalescent with 6H, 15R or 4H, the relations of the arrangement of their diffraction points has been derived. It is proved that there are twelve kinds of relation for the coalescence of xH with 6H, thirty for xH with 15R and eight for xH with 4H. The relations and the formulas which are given in this paper for the calculation of the numbers of hexagonal packed layers in unit cell of xH may be applied not only to the Laue technique but also to other x-ray techniques.A great number of single crystals of silicon carbide grown in laboratory by the sublimating procedure and of technical silicon carbide had been studied. Seven new hexagonal types 141H, 80H, 58H, 55H, 15H, 9H and 7H were found. The space group of all these new polytypes was determined to be C3m, and their lattice parameters c in the hexagonal cell are 355.26?, 201.57?, 146.14?, 138.58?, 37.794?, 22.676? and 17.637? respectively.