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Evolution of molecular ordering and phase transitions in C 60 /C 70 solid solutions
Author(s) -
RuedaMorales Gabriela,
OrtizLópez Jaime
Publication year - 2004
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.200301944
Subject(s) - sublimation (psychology) , crystallite , miscibility , phase transition , atmospheric temperature range , solid solution , crystallography , phase (matter) , materials science , calorimetry , diffraction , dipole , fullerene , thermodynamics , chemistry , polymer , organic chemistry , psychology , physics , optics , metallurgy , composite material , psychotherapist
Polycrystalline solid solutions (C 60 ) x :(C 70 ) 1− x with 0 ≤ x ≤ 1 grown by sublimation are studied with AC calorimetry in the 5–300 K temperature range and with X‐ray powder diffraction at room temperature. For concentrations 0.15 ≤ x ≤ 0.68, an hexagonal disordered (hcp) single phase is found at room temperature with no evidence of phase transitions occurring down to 5 K. This is indication of complete C 60 /C 70 miscibility and of freezing of orientational disorder at low temperature for this concentration range. Phase transitions below room temperature are detected only for concentrations close to the pure fullerenes, with critical temperatures decreasing as x departs away from x = 0 and 1. The elastic dipole model is applied in pure C 70 and C 70 ‐rich solid solutions to account for elastic interactions and ferroelastic ordering of the elongated C 70 molecule. Within this model, the evolution of ferroelastic phase transitions in C 70 ‐rich solid solutions is obtained and compared with available experimental data. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)