Effects of compressive stress on the dielectric properties of PMN-PT ceramics were investigated. The ceramics with the formulawere prepared by a conventional mixed-oxide method and then characterized with x-ray diffraction (XRD) and scanning electron microscopy. Dense perovskite-phase PMN-PT ceramics with uniform microstructure were successfully obtained. The dielectric properties under compressive stress were observed at stress up to 230 MPa using a home-built compressometer. The experimental results revealed that the superimposed compression stress significantly reduced both the dielectric constant and the dielectric loss tangent of 0.9PMN-0.1PT ceramic, while the changes were not as significant in the other PMN-PT ceramic compositions. In addition, the dielectric properties were considerably lowered after a stress cycle. Since change in the dielectric properties with applied stress was attributed to the competing influences of the intrinsic and the extrinsic contributions, the observations were mainly interpreted in terms of domain switching through non-180 • domain walls, de-ageing, clamping of domain walls and the stress induced decrease in the switchable part of spontaneous polarization.

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Effects of compressive stress on the ferroelectric properties of Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN-PT) ceramics were investigated. The ceramics with the formula (1−x)Pb(Mg1/3Nb2/3)O3−(x)PbTiO3 or (1−x)PMN−(x)PT (x=0.1–0.5) were prepared by a conventional mixed-oxide method. Dense perovskite-phase PMN-PT ceramics with a uniform microstructure were obtained. The ferroelectric properties were measured under compressive stress (0–75 MPa) using a homebuilt compressometer in conjunction with a modified Sawyer–Tower circuit. The experimental results revealed that the superimposed compression stress significantly reduced both the dissipation energy and the polarizations of the near morphotropic phase boundary compositions, i.e., 0.8PMN-0.2PT, 0.7PMN-0.3PT, and 0.6PMN-0.4PT, while the stress influence was much less in other compositions. On the contrary, the applied compressive stress showed little or no influence on the coercive field. These results were interpreted through the non-180° ferroelastic domain switching processes and the stress induced decrease in the switchable part of domains.

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The (1 -x)BiFeO 3 -xBaTiO 3 (with x = 0.1, 0.2, 0.3, and 0.4) ceramics were fabricated successfully by solid-state reaction method. Single-phase perovskite was obtained in all ceramics, as confirmed by XRD technique. It was observed that 0.7BiFeO 3 -0.3BaTiO 3 was the morphotropic phase boundary (MPB) between rhombohedral and cubic phases, as also revealed from ferroelectric and magnetic properties. The simulated and experimental X-Ray Absorption Spectroscopy (XAS) study revealed that BT in 0.75BF-0.25BT is possibly taken a rhombohedral structure. Furthermore, the rounded ferroelectric hysteresis loops observed for 0.9BiFeO 3 -0.1BaTiO 3 and 0.8BiFeO 3 -0.2BaTiO 3 compositions could be attributed to their microstructure and surface charge effects and electron transfer between Fe 3+ and Fe 2+ ions. It was also found that high dielectric constant of 0.9BiFeO 3 -0.1BaTiO 3 composition was a result of grain and grain-boundary effects, as observed in SEM micrographs. In addition, a strong signature of dielectric relaxation behavior was observed in this ceramic system with the activation energy 0.467 eV obtained from the Arrhenius' law. Finally, the local structure investigation with XAS technique provided additional information to better understand the electric and magnetic properties in the BF-BT ceramic system.

The influences of compressive stress on the dielectric and ferroelectric properties of Fe3+/Nb5+ hybrid-doped barium titanate (BaTiO3) ceramics were investigated. Superimposed compressive stress had a pronounced effect on the electrical properties of the ceramics. The response of low-field dielectric properties to stress changed from soft to hard piezoelectric behavior with increasing Nb5+ content. While ferroelectric properties decreased with stress, hardening behavior was observed with increasing Nb5+ content in hybrid-doped BaTiO3 ceramics. A mechanism based on induced change in the acceptor valence by the donor dopant in hybrid-doped BaTiO3 ceramics was proposed to explain the results obtained.