Особенности структуры промежуточной фазы в цирконате-титанате свинца с высоким содержанием циркония

Results of X-ray diffraction in the intermediate ferroelectric phase of single crystal PbZr$_{0.993}$Ti$_{0.007}$O$_{3}$ are presented. Existence of M-type superstructures $q_{M}$ = \{$\frac{1}{2}$, $\frac{1}{2}$, 0\} and satellites around them, $q_{M}+\{\delta,\delta,\delta\}$, is confirmed. For the first time second order satellites $\{2\delta,2\delta,2\delta\}$ have been observed in the vicinity of $q_{M}$ and fundamental Bragg peaks. Structural model of regular system of antiphase domains is used for diffraction calculation. Calculated pattern includes M-type superstructures as well as first and second order satellites around $q_{M}$. It is shown that second order satellites around fundamental Bragg peaks could not be reproduced in the context of this model. The possible origin of the system of the superstructure reflection observed in the intermediate phase is discussed.

Магнитные свойства слоистого кобальтита Sr-=SUB=-1-x-=/SUB=-Y-=SUB=-x-=/SUB=-CoO-=SUB=-3-delta-=/SUB=- (x = 0.1)

The structure, the magnetic and magnetotransport properties of perovskite Sr_0.9Y_0.1CoO_2.63 have been studied. The sample is shown to have a two-phase structure. The main phase has a tetragonally distorted unit cell and is described by space group I 4/ mmm . The broadening of the reflections with indices corresponding to doubling unit cell parameter c indicates the absence of the rigorous translation symmetry along axis c . The existence of the broadened superstructure reflection observed in the diffraction pattern at small angles at temperature lower than 400 K is explained by the existence of the monoclinic phase whose content is significantly lower than that of the tetragonal phase, but is dominant in the Sr_0.8Y_0.2CoO_3–δ composition. The spontaneous magnetization appears as the monoclinic phase forms. The magnetic structure is mainly G-type antiferromagnetic with magnetic moments 1.5μ_B in the layers of CoO_6 octahedra and 2μ_B in the anion-deficit CoO_4 + γ layers. The conduction of the Sr_0.9Y_0.1CoO_2.63 composition has a semiconducting character. The magnetoresistance is 57% in a field of 14 T at a temperature of 5 K and strongly decreases with the temperature increase.

Dielectric Properties and Long-Range Structural Order in (x)Pb(In1/2Nb1/2)O3:(1-x)Pb(Mg1/3Nb2/3)O3 Relaxor Ceramics

ABSTRACTThe relative permittivity of (x)Pb(In1/2Nb1/2)O3:(1-x)Pb(Mg1/3Nb2/3)O3 ceramics with compositions x=0.1, 0.3 and 0.6 were found to exhibit relaxor behavior. The maximum values of the relative permittivity at 100 Hz were ∼ 6500 at -2°C, 4000 at 5°C and 3700 at 15°C for x=0.1, 0.3 and 0.6, respectively. The 1:1 structural long-range ordering and forbidden reflections were studied by transmission electron microscopy. The size of the ordered domains increased with increasing Pb(In1/2Nb1/2)O3. In addition to the superstructure reflection 1/2 1/2 1/2, the forbidden reflection 1/2 1/2 0 and streaking were observed.