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Direct evidence for Vogel-Fulcher freezing in relaxor ferroelectrics

Direct evidence for freezing in two relaxer ferroelectrics, PbMg1/3Nb2/3O3 and PbSc1/2Ta1/2O3, at a certain temperature T-f not equal 0K was obtained from the temperature dependence of the maximum relaxation time, tau(max), It was shown that tau(max)(T) follows the Vogel-Fulcher (VF) law, and tends toward infinity as temperature approaches T-f. The freezing temperature T-f derived from tau(max)(T) coincides with the value of T-f obtained from the fit of frequency, omega, dependence of the temperature, T-max, of the dielectric permittivity maximum to the same VF law. Thus, this result solves the controversy that the VF law for omega(T-max) may not correspond to the freezing of the spectrum. (C) 1998 American Institute of Physics.

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