Abstract
The thermodynaqmics for intercalation of phenanthrene (PHN) with Ba, for which superconductivity has been reported, is studied in comparison with its isomer of a linear aromatic hydrocarbon of anthracene (AN). Contrary to previous reports by other authors, the important observation that Ba is intercalated into neither PHN nor AN without affecting their molecular structures is unambiguously made by differential scanning calorimetry measurements and annealing time dependences observed by powder x-ray diffraction (XRD) measurements. The reactions of Ba and PHN at elevated temperatures lead this system to molecular decomposition instead of intercalation, resulting in the carbide or amorphous carbon formation, which is clearly supported by XRD and Raman spectroscopy. The phenomena of metallicity and superconductivity in PHN intercalated with alkaline-earth metals (Ba or Sr) should be reconsidered.
- Received 16 July 2014
- Revised 3 October 2014
DOI:https://doi.org/10.1103/PhysRevB.90.134519
©2014 American Physical Society