NMR investigation of mixed relaxors x PMN-(1 — x)PSN

Abstract

Measurement of 93Nb, 45Sc, 207Pb NMR spectra are performed for the first time in the solid solution of the ferroelectric relaxors xPMN-(1 — x) PSN (0 ≤ x ≤ 1). The peculiar behavior of the observed quantities and parameters, e.g. disappearance of dielectric dispersion for x ≈ 0.5, was explained by NMR measurements for the first time. The analysis of 45Sc NMR spectra dependence on x has shown that for x > 0.5 the ordering of the regions containing Sc ions takes place. The dependence of the level of structural order on solid solution composition is obtained. The investigation and analysis of temperature dependence of 93Nb and 45Sc NMR line width of the end member of the considered solid solution PSN made it possible to obtain new information about ions shifts and dynamics. It was shown that at T < Tmax Nb and Sc ions are shifted from their equilibrium lattice site (Tmax is dielectric permittivity ε′ maximum position). These ions shifts contribute to the temperature dependence of lattice polarization P, meanwhile jump of P at T = Tmax is determined by Pb ions shifts. The Nb ions electric diploes were shown to be static in PSN in NMR measurements scale (10−7 s) contrary to essential Nb dipoles reorientation dynamic behavior in PMN. The peculiarities of NMR line form in the investigated materials gave evidence about distribution of Nb, Sc, Pb dipole moments directions as well as values at any constant temperature.