Peculiarities of dielectric response of 1:1 family relaxors

Abstract

A mixed ferroglass phase with coexistence of long and short range order was proposed as the model for quantitative description of the 1:1 family relaxors. Calculations of dielectric response of these relaxors were performed in the random field theory framework. Four and three groups of maxima were obtained in the dielectric permittivity temperature dependence at several frequencies for less and more ordered samples respectively. The frequency dependence of maxima at the lowest temperatures was shown to obey the Vogel-Fulcher (V-F) law, whereas other maxima the Arrhenius law. The peculiar feature of more ordered relaxors was shown to be the proximity of freezing temperature Tg to the temperature of maximum position Tm. Measurement of dielectric response of Pb(Sc0.5Nb0.2Ta0.3)O3 (PSNT) single crystals revealed two groups of maxima, one at T310 K and another at T>330 K. The frequency dependences of low temperature maxima and high temperature ones were shown to obey the V-F law with Tg = 292.5 K and the Arrhenius law with activation energy 0.49 eV. The comparison of obtained experimental data for PSNT as well as those for two samples of PbSc1/2Ta1/2O3 exhibiting different levels of order with the theory have shown that a mixed ferroglass model with different ratio of long and short range order describes fairly well the main peculiarities of the dielectric response of the 1:1 family relaxors.

High-pressure peculiarities in compositionally ordered Pb(Sc1/2Nb1/2)O3

“…A similar effect was observed in the electron-and neutrondiffraction experiments on PbZr 1−x Ti x O 3 perovskite compounds [19,20]. The conception of two coexisting contributions to the short/long-range ferroelectric orders seems to correspond to the theoretical model of mixed ferro-glass [21] proposed for 1:1 ferroelectric relaxors.…”

Dielectric properties of fine-grained triglycine sulphate (TGS)

“…Our data for TGS, powdered and pressed in epoxy glue after a preliminary powder segregation, represent an experimental probe of the T c distribution and remind the dynamical properties of relaxor ferroelectrics theoretically analysed by M. D. Glinchuk et al [20]. Distinct maxima (local T c ) can be seen in Fig.…”

Low temperature short-range ordering caused by Mn2 +doping of Rb3H(SO4)2

“…It has been shown in [22] that the dielectric response versus temperature in a mixed ferroglass phase reveals frequencydependent maxima. The position T m of a maximum in the temperature scale can be analysed with the help of the formula: where τ 0 and V are the pre-exponential factor and the barrier height in the expression for the temperature dependence of the relaxor relaxation time, respectively.…”