Synthesis, Structural Characterization, and Properties of Perovskites Belonging to the xBiMnO3−(1 − x) PbTiO3 System

The xBiMnO3−(1 − x) PbTiO3 solid solution has been synthesized by an accurate, nonclassical, wet-chemistry method. Results show the existence of two structurally different perovskites, depending on the x value: tetragonal for 0≤ x <0.36; pseudocubic for 0.44< x ≤0.8; and a morphotropic phase boundary (MPB) between both symmetries for 0.36≤ x ≤0.44. When x ≥ 0.76, unidentified diffraction lines appear together with those of the perovskite. The evolution of the unit-cell parameters has been studied by X-ray diffraction techniques. The stability of different symmetries can be correlated with the Goldschmidt’s tolerance factors (t) for perovskites, with the MPB only existing for a critical t ≈ 1.00 value. Materials with x ≤ 0.4 exhibit the ferroelectric transition above room temperature; their Curie temperatures have been determined by thermal analysis, dielectric versus temperature measurements, and dynamical−mechanical analysis. This temperature decreases as the bismuth and manganese contents increase, bein...