DIELECTRIC AGEING IN LAYERED FERROELECTRICS

ABSTRACT

Studies of the effects of sample history on long-term relaxation of polarization in the Na_0.5Bi_8.5Ti₂Nb₄O₂₇ and Na_0.5Bi_8.5Ti₂Ta₄O₂₇ ferroelectrics of layered structures are reported. The type of functional relationship of ε′(t) at measuring procedures including heating or cooling to the temperature being examined T_a is found to change from exponential (Kohlrausch function) to logarithmic. Results are discussed within the assumption of presence of defect complexes in disordered ferroelectrics.

Keywords:

• ceramics
• layered structures
• dielectric spectroscopy
• phase transitions

ACKNOWLEDGMENT

This work was supported by Latvian Council of Science, project number 05.1864 and grant of Russian Ministry of Education No: E02-3.4-424 and grant No: 02-02-16232.