Phase transitions in N—n-propylpyridinium-TCNQ2 and N—n-butylpyridinium-TCNQn at high pressures |
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| Authors: | I. Shirotani S. Yoshida Y. Wada T. Kajiwara M. Murakami S. Yoshimura |
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| Affiliation: | 1. The Institute for Solid State Physics, The University of Tokyo, Roppongi, Minato-ku, Tokyo 106, Japan;2. Department of Chemistry, Faculty of Science, Toho University, Miyama, Funabashi 274, Japan;3. Matsushita Research Institute Tokyo, Inc., Ikuta, Tama-ku, Kawasaki 214, Japan |
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| Abstract: | The electrical resistivity of N-n-propylpyridinium-TCNQ2 (NPPy-TCNQ2) and N-n-butylpyridinium-TCNQn (NBPy-TCNQn) has been measured as a function of temperature and pressure. Phase transitions in these salts have been studied at high pressures. The transition temperature (Tc) in NPPy-TCNQ2 at atmospheric pressure increased with increasing pressure at the rate of dTc/dP = + 12.0 degkbar?1. The value of volume change calculated from the Clapeylon-Clausius relation was + 4.4 cm3 mol?1. The electrical resistivity along the a- and c-axis increased with increasing pressure below 7 kbar. This anomalous electrical behaviour is closely related to the crystal structure of NPPy-TCNQ2. The resistivity dropped sharply at about 11 kbar. This abrupt change may be due to a new pressure induced phase transition.The Tc of the NBPy-TCNQn increased remarkably with increasing pressure up to 0.7 kbar, above which the phase transition disappeared. The phase transitions of N-n-alkyl-substituted pyridinium TCNQ salts depend strongly on the nature of cations. |
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