Индуцированный фазовый переход в монокристаллических твердых растворах PbMg-=SUB=-1/3-=/SUB=-Nb-=SUB=-2/3-=/SUB=-O-=SUB=-3-=/SUB=--29PbTiO-=SUB=-3-=/SUB=- и PbZn-=SUB=-1/3-=/SUB=-Nb-=SUB=-2/3-=/SUB=-O-=SUB=-3-=/SUB=--9PbTiO-=SUB=-3-=/SUB=-: сходство и различие

The kinetics of the induced phase transition in single-crystal relaxor solid solutions PbMg1 / 3Nb2 / 3O3-29PbTiO3 and PbZn1 / 3Nb2 / 3O3-9PbTiO3 is studied when an electric field is applied along the [001] direction. At temperatures below the temperature of the morphotropic phase transition, the changes in the dielectric constant and optical transmission in electric fields are studied. It is shown that the decrease in optical transmission with time is associated only with a change in the sizes of nanoregions during the phase transition. It was found that the induced phase transition proceeds differently in these crystals. In PMN-29PT crystals, the formation of ferroelectric phases and the rapid establishment of macroscopic polarization are preceded by a certain delay time, while in PZN-9PT crystals, the ferroelectric phase is induced immediately after the application of the field without a delay time. The results obtained are explained by the different structures of the low-temperature phases in these compounds. Key words: ferroelectricity, relaxors, induced phase transition.

Поведение керамических твердых растворов 33PbYb-=SUB=-1/2-=/SUB=-Nb-=SUB=-1/2-=/SUB=-O-=SUB=-3-=/SUB=--22PbZrO-=SUB=-3-=/SUB=--45PbTiO-=SUB=-3-=/SUB=- в электрическом поле

The temperature dependences of the dielectric parameters were studied, as well as the changes in the dielectric constant with time in ceramic 33PbYb1 / 2Nb1 / 2O3-22PbZrO3-45 PbTiO3 samples in electric fields (0 <E <8 kV / cm). It is shown that in the phase existing below the temperature of the morphotropic phase transition, in addition to the rhombohedral and tetragonal phases, a small fraction of the relaxor pseudocubic phase is present. It was found that, unlike other relaxors, the dielectric constant practically does not change with time when an electric field is applied in the phase below the temperature of the morphotropic phase transition. Possible reasons for this behavior are discussed.

Магнитострикционные аномалии редкоземельных фаз Лавеса c морфотропным фазовым переходом

Оver recent years in the process of searching for compounds with high or almost zero magnetostriction values, a number of pseudo-binary Laves RT2 phases with morphotropic phase transitions are attracted particular attention. That is, systems of compounds with a morphotropic phase boundary in the phase diagram. In this paper, the magnetic and magnetostrictive properties of multicomponent systems of compounds Tb0.2Dy0.8-хGdxCo2 and Tb0.2Dy0.8-хGdxCo1.9Al0.1 in which a morphotropic phase transition is observed when replacing dysprosium with gadolinium have been studied. A relationship between the temperature behavior, the sign and magnitude of magnetostrictive deformations, and the type of distortion of the cubic lattice of the studied Laves phases is revealed. In the region of magnetic phase transitions, the magnetocaloric effect was investigated.