DIELECTRIC AGEING IN LAYERED FERROELECTRICS

ABSTRACT Studies of the effects of sample history on long-term relaxation of polarization in the Na0.5Bi8.5Ti2Nb4O27 and Na0.5Bi8.5Ti2Ta4O27 ferroelectrics of layered structures are reported. The type of functional relationship of e′(t) at measuring procedures including heating or cooling to the temperature being examined Ta is found to change from exponential (Kohlrausch function) to logarithmic. Results are discussed within the assumption of presence of defect complexes in disordered ferroelectrics.