Papers by Keyword: Antiferroelectric

Abstract: We have studied temperature-induced phase transitions in PbZrO₃ thin films by X-ray diffraction. By tracing the temperature dependence of superstructure reflections we show that the onset of antiferroelectric ordering takes place highly continuously on cooling and another, presumably ferroelectric phase is present at high temperatures, between the antiferroelectric and cubic phases. To clarify the possible reason for this behavior, we have investigated the X-ray diffraction profile with momentum transfer along the normal to the film surface and carried out the relevant simulation using the formalism of scattering by inhomogeneously deformed sample. From the analysis it follows that the near-interface layer is effectively compressed along the normal to the film. We associate this observation with the presence of dislocations through which the film is relaxed. The results suggest that the reasons for the phase transition sequence modification in thin films can be associated with inhomogeneous distribution of stress and defects in the near-interface area.

Abstract: Lead hafnate single crystals were characterized using single crystal x-ray diffraction under simultaneous application of hydrostatic pressure and high temperatures. The information on the structure of two intermediate phases, situated between antiferroelectric and paraelectric phases in the pressure-temperature phase diagram, has been obtained. The lower-temperature intermediate phase is characterized by incommensurate displacive modulations in Pb sublattice. The higher-temperature intermediate phase is characterized by oxygen framework distortion, primarily in the form of anti-phase tilts of the oxygen octahedra, which is also present in the lower-temperature intermediate phase.

Abstract: (Pb0.97La0.02)(Zr0.92-xSnxTi0.08)O3 (PLZST) ferroelectric ceramics with x=0.40, 0.25, 0.15, respectively, were investigated. It was found that these ceramics with different Zr:Sn ratios were perovskite structure. With increasing of Zr:Sn ratio, the phase-transition electric-field of antiferroelectric to ferroelectric phase increased. when x>0.15,All the samples have double hysteresis loops with antiferroelectric phase characteristics. Yet, when the electric field was removed at lower temperature of -5oC and -20oC, for x=0.25 and 0.40, the electric field induced FE phase can remain metastable FE state. But for x=0.15, the induced FE phase recover to AFE phase even at -20oC. Yet, electric field induced FE phase exist as metastable FE phase. TFE-AFE of the samples was -5oC, -20oC, when x=0.40, x=0.25, respectively. With increasing of Zr:Sn ratio, TFE-AFE increaseddecreased, Tc was hardly changed, but the dielectric constant increased from ~2500 to ~6000, the peak changed sharply, dielectric loss increased continuously with increasing of Zr:Sn ratio.

Abstract: The effects of alumina nanoparticles on the properties of PbZrO3 ceramics were investigated. The samples were prepared by a simple conventional mixed oxide method involving calcination and sintering temperatures of 800 oC and 1200 oC, respectively. Single-phase lead zirconate was observed in X-ray powder diffraction patterns for all the samples. The relationship between the Al2O3 content, the dielectric properties and Knoop hardness were determined. The results indicate that the additive affects Curie temperatures and the shape of the Curie peak, implying a chemical reaction takes place with the matrix during high-temperature processing. Hardness values increase for additions up to 1 vol % Al2O3.

Abstract: Bipolar electric fatigue in antiferroelectrics of the lead zirconate titanate stannate ceramics family was investigated. Variations in strain hysteresis loops and damages in microstructure of the materials due to the electric cycling were analyzed. The materials showed symmetric or asymmetric suppression of strain hysteresis loop, normal or diffuse AFE-FE phase transition and intact or damaged microstructure after 5×10-7 cycles, indicating a strong composition dependent fatigue effect and the corresponding mechanism. In general, the antiferroelectric materials exhibited much higher fatigue resistance than ferroelectric ceramics reported previously.