Electrical conductivity, magnetoresistance, and hall coefficient in the course of bromination of graphite and ammonia absorption by potassium-graphite intercalation compounds

✍ Scribed by Noboru Akuzawa; Seiji Takei; Mahito Yoshioka; Yoichi Takahashi

• Publisher: Elsevier Science
• Year: 1991
• Tongue: English
• Weight: 416 KB
• Volume: 29
• Category: Article
• ISSN: 0008-6223
• DOI: 10.1016/0008-6223(91)90166-g

✦ Synopsis

Electrical conductivity, transverse magnetoresistance, and Hall coefficient, both of graphite in the course of bromination and of potassium-graphite intercalation compounds (K-GICs) in the course of ammoniation, were determined. Concentrations and mobilities of holes and electrons (q,, it,, p+, kc) for graphite-bromine intercalation compounds were determined as a function of the bromine content, BrlC. As BrlC increases, both nh and )*e increase, while n, and kh decrease. The value of the product nh p+ increases with Br/C, but q.~, decreases. The increase of conductivity of graphite by bromination is confirmed to be a reflection of the increase in nh. in agreement with the previous investigation by Marchand and Mathur.

The conductivity and Hall coefficient of KC, were also determined as a function of NHJK, but the magnetoresistance was too small to be detected. The mean carrier concentration, ii, and the mean carrier mobility, F;, were estimated as a function of NHJK: E increases with the increase of NHJK, while jI decreases with NHJK. It was found that the effect of the decrease of ii is larger than that of the increase of F, resulting in the decrease of conductivity found with KC, as it is ammoniated. These results were attributed to backdonation of free electrons form the carbon n* band to the intercalated layers, caused by the increase of the interlayer distance when potassium ions are solvated by ammonia molecules.