New morphotropic phase boundary (MPB) piezoelectrics, with ferroelectric phase transition (T c ) exceeding that of PbZrO 3 -PbTiO 3 (PZT), were investigated. Based on a perovskite tolerance factor-T c relationship, new high T c MPB systems were projected in the Bi(Me)O 3 -PbTiO 3 system, where Me is a relatively large B +3 -site cation. For the (1 − x)BiScO 3 -(x)PbTiO 3 solid solution, a MPB was found at x-0.64 separating the rhombohedral and tetragonal phases, with correspondingly enhanced dielectric and piezoelectric properties. A transition temperature T c of ∼ 450 • C was determined with evidence of T c 's on the order of ≥ 600 • C in the BiInO 3 and BiYbO 3 analogues, though issues of perovskite stability remain for the smaller tolerance end-member systems.

No abstract

In the current work, the bulk (1−x)BiFeO3–xBaTiO3 system has been studied as a potential lead‐free piezoelectric material. Barium titanate (BaTiO3) in solid solution with bismuth ferrite (BiFeO3) is observed to stabilize the perovskite structure and improve switching behavior. Samples with various content of BaTiO3 were prepared via solid‐state route, and pure perovskite phase was confirmed by X‐ray diffraction. Modification of the BaTiO3–BiFeO3 material with Mn improved DC resistivity by one to five orders of magnitude (7.6 × 1012 vs. 2.7 × 107Ω·m for 25 mol% BaTiO3 at room temperature) and polarization hysteresis measurements indicated “hard” ferroelectric behavior with the highest strain response at 33 mol% BaTiO3. Finally, low‐field piezoelectric d33 coefficient of 116 pC/N and ferroelectric transition temperature above 450°C are reported for 25 mol% BaTiO3 composition.

(1−x) Bi(Mg 1/2 Ti 1/2 ) O 3 –x PbTiO 3 polycrystalline ceramics were investigated for potential as high-temperature piezoelectric materials. A morphotropic phase boundary (MPB) between tetragonal (T) and rhombohedral (R) ferroelectric (FE) phases, which exhibited enhanced piezoelectric activity and a ferroelectric–paraelectric phase transition at 478 °C was observed at x≈0.37. Electron diffraction patterns (x⩽0.37) contained discrete superlattice reflections at 12{hkl} positions arising from antiphase rotations of the O octahedra, consistent with R3c space group symmetry. These reflections were diffuse at the MPB (x=0.38) and absent in the T phase (x=0.5). In the unpoled state, FE R (x=0.35) ceramics revealed a polar microdomain structure whereas the T phase (x=0.5) contained classic {110} twin domain boundaries. However, poled R samples underwent a field-induced transformation to an aligned domain structure with {110} twin boundaries similar to those in the T phase. Correlations are made between structure and properties for these piezoelectric materials.