Low-Temperature Dielectric Response of Relaxor Ferroelectrics and Related Disordered Materials

Abstract

This paper reviews the characteristic dielectric dispersion of relaxor ferroelectrics PbMg_⅓Nb_2/3O₃, and (Pb_{1- x} La _x )(Zr _y Ti_1-y )_1-x/4O₃ and ferroelectric BiScO₃-PbTiO₃ solid solutions in the frequency range of 100 Hz–2 THz. In relaxors the main dielectric dispersion at high temperatures appears in the microwave and mm-wave region, which softens and broadens on cooling. Distribution of relaxation times below room temperature is very broad and below freezing temperature it results in nearly frequency independent dielectric loss in the entire available frequency range. The broad distribution of relaxation times stems from structural inhomogeneities which cause random fields and have influence on the distribution of activation energies for hopping of disordered ions. Landau-type thermodynamic model was proposed for explanation of the distribution of relaxation times. Besides the frequency independent dielectric loss, additional dielectric relaxation of not thermally activated origin was observed in BiScO₃-64%PbTiO₃ below 1 GHz.

Keywords:

• Dielectric spectroscopy
• relaxor ferroelectrics
• dielectric loss