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Secondary relaxations of orientationally disordered mixed crystals at temperatures lower than the glass transition temperature
Author(s) -
MartinezGarcia J. C.,
Tamarit J. Ll.,
Pardo L. C.,
Barrio M.,
Rzoska S. J.,
DrozdRzoska A.
Publication year - 2011
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201000726
Subject(s) - glass transition , relaxation (psychology) , dielectric , permittivity , intramolecular force , work (physics) , condensed matter physics , thermodynamics , materials science , chemistry , chemical physics , physics , stereochemistry , composite material , polymer , psychology , social psychology , optoelectronics
Low‐molecular weight cyclic alcohols as cycloheptanol (C 7 H 14 O, hereinafter referred to as cC7‐ol) and cyclooctanol (C 8 H 16 O, cC8‐ol) are prototypical materials displaying OD phases which, under fast cooling give rise to orientational glasses (OG). In addition to the ubiquitous α ‐relaxation of canonical glasses, several secondary relaxations appear for the mentioned systems ( β and γ for cC8‐ol and β for cC7‐ol). The intramolecular character of these secondary relaxations for these materials as well as their mixed crystals was highlighted at temperatures close but above the glass transition. For lower temperatures the low values of dielectric strength makes difficult to account for the relaxation times obtained from the permittivity losses and, thus in this work we present a data analysis based on the Kramers–Kronig relations which connect the real and imaginary parts of dielectric permittivity and shows up a new method to make evident the existence of such secondary relaxations as well as to avoid phenomenological equations for determining the relaxation time.