Dynamic dielectric permittivity of 1 : 1 family relaxors

Measurements of dielectric response of Pb(Sc0.5Nb0.2Ta0.3)O-3 (PSNT) single crystals revealed two groups of maxima, one at T approximate to 310 K and another at T > 336 K. The frequency dependence of low temperature maxima an d high temperature ones are shown to obey the (V-F) Vogel-Fulcher law with T-g= 292.5 K and the Arrenius law with activation energy 0.49 eV. A mixed ferroglass phase with coexistance of long and shea range order is p roposed as the model for the quantitative description of the 1:1 family rel axors. Several groups of maxima were obtained in the dielectric permittivit y dependence on temperature and frequency. The frequency dependence of maxi ma at the lowest temperatures are shown to obey the V-F Vogel-Fulcher law, whereas other maxima obey the Arrenius law. The peculiar feature of more or dered relaxors is shown to be the proximity of freezing temperature T-g to the temperature of permittivity maximum position T-m. The comparison of the 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 the mixed ferroglass model with different ratio of long and short range order describes the main peculiarities of the diel ectric response of the 1:1 family relaxors.