Wydział Chemii

Olaf Czupiński

Grażyna Bator

Zbigniew Ciunik

Ryszard Jakubas

Wojciech Medycki

J. Świergiel

2002

Journal of Physics-Condensed Matter

14

8497-8512

10.1088/0953-8984/14/36/308

Naukowa

Angielski

Artykuł

The crystal structure of the 4-aminopyridinium perchlorate (4-apyH)ClO₄ has been determined at 100 K by means of x-ray diffraction as monoclinic, with space group P 2₁, with Z = 8. The crystal undergoes two structural phase transitions: one of first-order type, reversible, at 241/243 K (on cooling/heating respectively) and one of weakly first-order type, irreversible, at 277 K (on heating). The crystal dynamics is discussed on the basis of the temperature dependence of the ¹ H nuclear magnetic resonance second moment (M₂) and spin–lattice relaxation time T₁. Both phase transitions are interpreted in terms of the changes in the motional state of (4-apyH)⁺ cations and ClO₄⁻ anions. The dielectric dispersion studies disclose a relaxation process over the high-temperature phase (above 241 K) in the audio-frequency region. The dielectric results are described by a Cole–Cole equation. The title crystal reveals pyroelectric properties below 241 K. The ferroelastic domain structure of (4-apyH)ClO₄ is observed over the whole temperature range studied

https://doi.org/10.1088/0953-8984/14/36/308

https://ioppublishing.org/