Thermal Diffusivity and Critical Behaviour of Uniaxial Ferroelectric Pb₅Ge₃O₁₁

Abstract

Thermal diffusivity of uniaxial ferroelectric Pb ₅ Ge ₃ O ₁₁ has been measured as a function of temperature using ac photopyroelectric calorimetry. The second order ferroelectric transition has been studied in order to ascertain the mechanisms which could explain the anomaly in specific heat through the study of the inverse of the thermal diffusivity. It has been shown that Pb ₅ Ge ₃ O ₁₁ falls within the universality class of the mean-field model: the ferroelectric phase is very well explained within the framework of the Landau model, while in the paralectric phase a logarithmic correction must be taken into account, as predicted by renormalization group theory.

Keywords:

• Critical phenomena
• ferroelectricity
• phase transition
• thermal diffusivity
• thermodynamic properties

Acknowledgments

This work has been supported by the University of the Basque Country through research grant No. EHU06/24.