Nokhrin S. Investigation of disordered ferroelectrics with perovskite structure by spectroscopic methods

The thtsis is devoted to investigation of local structure, dynamics peculiarities and ordering of the disordering ferroelectrics by NMR and dielectric spectroscopy methods. The absence of the ion ordering 1:1 and niobium-rich regions have been shown in lead magnesium niobate by analysing NMR line shape peculiarities; the existence of microregions with ion ordering 1:2 was revealed. The NMR line shape of niobium in potassium tantalate with niobium was analysed and the behaviour of niobium impurity have been studied as was conditioned by dynamics of elastic dipole moments. Lack of local phase transition ion of niobium in the off-central position was found. The local structure of solid solution of relaxor ferroelectrics lead magnoniobate-scandoniobate have been studied and was shown its ordering at concentration 50% by NMR and dielectric spectroscopy methods. The influence of lantanium on the properties lead zirconate ceramics was studied; La impurities can be considered asthe perturbation, which results into decreasing of temperature Curie and therefore in dielectric susceptibility decreasing. Low-frequency dispertion of dielectric susceptibility was observed in antiferroelectric phase of lead zirconate for the first time.