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Abstract
The temperature of the dielectric constant (DC) maximum of relaxor ferroelectrics (fully cubically stabilized paraelectrics)1,2 as, e.g., PMN decreases with decreasing frequency of the measuring field so that the maximum of a static DC is not defined (cf, e.g., Reference 1). On PLZT 8/65/35 ceramics, however, a frequency dependence of the DC maximum temperature can be observed only above about 10 kHz.3 This peculiarity is assumed to be caused by aging that is well known to decrease the low-frequency dielectric dispersion.3 We assumed that no aging would take place when the sample is cooled down from temperatures well above the DC maxima while a triangular field Eb with finite amplitude is applied. The DC taken in this way for Eb = 0 depends similarly on the temperature and frequency as observed for PMN and SBN (e.g., Reference 4). Even in this case, however, the field dependence of the DC shows a minimum for Eb = 0. A possible cause of this peculiarity is suggested to be a competition between different kinds of short-range order.