Raman Response of Quantum Critical Ferroelectric Pb-Doped SrTiO3

A quantum paraelectric SrTiO3 is a material situated in close proximity to a quantum critical point (QCP) of ferroelectric transition in which the critical temperature to the ferroelectric state is suppressed down to 0 K. However, the understanding of the behavior of the phase transition in the vicinity of this point remains challenging. Using the concentration x of Pb in solid solution Sr1−xPbxTiO3 (PSTx) as a tuning parameter and applying the combination of Raman and dielectric spectroscopy methods, we approach the QCP in PSTx and study the interplay of classical and quantum phenomena in the region of criticality. We obtain the critical temperature of PSTx and the evolution of the temperature-dependent dynamical properties of the system as a function of x to reveal the mechanism of the transition. We show that the ferroelectric transition occurs gradually through the emergence of the polar nanoregions inside the non-polar tetragonal phase with their further expansion on cooling. We also study the ferroelastic cubic-to-tetragonal structural transition, occurring at higher temperatures, and show that its properties are almost concentration-independent and not affected by the quantum criticality.

Phase transition in an organic ferroelectric: glycinium phosphite, with and without X-ray radiation damage

Thermal evolution of an organic ferroelectric, namely, glycinium phosphite, was probed by multi-temperature single-crystal diffraction using synchrotron radiation and also by a similar experiment with a laboratory X-ray diffractometer. Both series of measurements showed a transition from the paraelectric to the ferroelectric state at nearly the same temperature, T c = 225 K. Temperature evolution of the unit-cell parameters and volume are drastically different for the synchrotron and laboratory data. The latter case corresponds to previous reports and shows an expected contraction of the cell on cooling. The data collected with the synchrotron beam show an abnormal nonlinear increase in volume on cooling. Structure analysis shows that this volume increase is accompanied by a suppression of scattering at high angles and an apparent increase of the anisotropic displacement parameters for all atoms; we therefore link these effects to radiation damage accumulated during consecutive data collections. The effects of radiation on the formation of the polar structure of ferroelectric glycinium phosphite is discussed together with the advantages and drawbacks of synchrotron experimentation with fine temperature sampling.

Effect of Composition on Polarization Hysteresis and Energy Storage Ability of P(VDF-TrFE-CFE) Relaxor Terpolymers

The temperature dependence of the dielectric permittivity and polarization hysteresis loops of P(VDF-TrFE-CFE) polymer films with different compositions are studied. Among them, the three compositions, 51.3/48.7/6.2, 59.8/40.2/7.3, and 70/30/8.1, are characterized for the first time. Relaxor behavior is confirmed for all studied samples. Increasing the CFE content results in lowering the freezing temperature and stabilizes the ergodic relaxor state. The observed double hysteresis loops are related to the field-induced transition to a ferroelectric state. The critical field corresponding to this transition varies with the composition and temperature; it becomes larger for temperatures far from the freezing temperature. The energy storage performance is evaluated from the analysis of unipolar polarization hysteresis loops. P(VDF-TrFE-CFE) 59.8/40.2/7.3 shows the largest energy density of about 5 J·cm−3 (at the field of 200 MV·m−1) and a charge–discharge efficiency of 63%, which iscomparable with the best literature data for the neat terpolymers.

Ferroelectric State and Polarization Switching Behaviour of Ultrafine BaTiO3 Nanoparticles with Large-Scale Size Uniformity

BaTiO3 (BTO) nanoparticles (NPs) with controlled particle sizes of 2.8, 4.5 and 8.1 nm and large-scale size uniformity are fabricated. The structure and polarization switching behaviour of the 4.5 nm...

Эффект модификации вклада термоэмиссии локализованных зарядов в релаксацию фотоотклика монокристалла TlGaSe-=SUB=-2-=/SUB=-

The studing of thermoemission process peculiarities from the of charge localization centers in electrically non-uniform TlGaSe2 crystal are presented. Heterogeneity was formed by preliminary polarization of a sample at low temperature of ferroelectric state of the crystal. The results are good agreement with peculiarities of the localized charges thermoemission registration on TlInS2 in the temperature region of ferroelectric state of the crystal.

Структура и сегнетоэлектрические свойства гетероэпитаксиальных тонких пленок NaNbO-=SUB=-3-=/SUB=-, полученных методом RF-катодного распыления

For the first time, thin films of NaNbO3 on a MgO(001) substrate, on which a SrRuO3 layer was previously deposited, were obtained by RF cathode sputtering in an oxygen atmosphere. According to x-ray diffraction analysis the films are single phase and single-crystalline. The lattice parameters in the tetragonal approximation for the NaNbO3 and SrRuO3 layers were: с(NaNbO3) = 0.3940(1) nm, a(NaNbO3) = 0.389(1) nm; с(SrRuO3) = 0.4004(1) nm, a(SrRuO3) = 0.392(3) nm. The unit cell deformation for NaNbO3 was ε33 = 0.007, ε11 = 0.002. Dielectric and piezoelectric measurements indicate that the films are in a ferroelectric state.

Realizing a ferroelectric state and high pyroelectric performance in antiferroelectric-oxide composites

We report a robust room temperature ferroelectric (FE) state in (1 − x)Pb0.99Nb0.02[(Zr0.57Sn0.43)0.933Ti0.067]0.98O3–xZnO ((1 − x)PNZST–xZnO) composites, where PNZST shows a predominant antiferroelectric (AFE) nature due to ZnO-induced internal strain.

DEPENDENCE OF THE STABILITY OF THE FERROELECTRIC PHASE OF POTASSIUM NITRATE IN A COMPOSITE WITH BARIUM TITANATE ON THE VOLUME AND SIZE OF INCLUSION PARTICLES

The results of a study of composites (KNO3) 1 -x /(BaTiO3)x (x = 0.1 and 0.2) are presented. It is shown that the stability of the ferroelectric state of potassium nitrate increases with an increase in the volume fraction of inclusions. It was found that the stability of the ferroelectric phase of potassium nitrate in the composite is also influenced by the particle size of the inclusions. It was revealed that the values of the dielectric constant in the region of the ferroelectric phase increase with an increase in the particle size of the inclusions.