Lattice Vibrations of Boron Carbides

✍ Scribed by P.A. Medwick; R.O. Pohl

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 304 KB
• Volume: 133
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1997.7314

✦ Synopsis

The internal friction at low temperatures has been measured on polycrystalline samples of -B, B 4 C, B 13 C 2 , and B 9 C. As the carbon deficiency increases in the boron carbides, the internal friction approaches that of amorphous solids. For comparison, the internal friction of amorphous B 9 C, produced as a thin film by e-beam evaporation on a Si double-paddle oscillator, has also been measured. It is very similar to that of the polycrystalline B 9 C sample. The results are discussed in terms of glass-like lattice vibrations which have been noted before in highly disordered crystals, e.g., Ba 1؊y La x F 2x . It is concluded that the low thermal conductivity of B 9 C near room temperature which has been observed previously is indeed equal to its theoretical lower limit.