Development of the front-detection photopyroelectric (FPPE) configuration for thermophysical study of glass-forming liquids

We report on the first frequency-dependent measurements of thermal effusivi ty of glass-forming liquids using the photopyroelectric (PPE) method. The a dvantage is higher modulation frequency capability than with previously rep orted methods. On the basis of our present results (up to 30 kHz), we find in the dispersion temperature region of glycerol a clear frequency-dependen ce of the real part and a non-zero, frequency-dependent imaginary part of t he thermal effusivity, which is consistent with literature data. The experi mental data reveal that the full exploitation of the high-frequency experim ental results requires to take into account also the piezoelectric componen t of the signal caused by the thermoelastic response of the sample. The hig h-frequency limit of this PPE experiment may be extended by a modified cell design and by using another pyroelectric material instead of a lithium tan talate crystalline sensor. (C) 2001 Elsevier Science B.V. All rights reserv ed.