Differential scanning calorimetry curves (heating) for (1−x)BiFeO3-(x)PbTiO3 samples. Inset: Zoom of the low temperature region (lower than 450 °C) evidencing the step-like changes in the DSC baseline.
(a) X-ray diffraction patterns at different temperatures, and (b) Rietveld refined lattice parameters and angles as a function of temperature, for the (0.75)BiFeO3-(0.25)PbTiO3 compound.
Differential scanning calorimetry signal and temperature dependence of the dielectric constant, ε′, for the (0.75)BiFeO3-(0.25)PbTiO3 compound.
Heating and cooling differential scanning calorimetric curves, and temperature dependent magnetization curves, for the (0.9)BiFeO3-(0.1)PbTiO3 compound. Inset: zoom of the differential scanning calorimetric curve around the Néel temperature.
High resolution image obtained by transmission electron microscopy in the tetragonal symmetry (P4mm space group) of the (0.6)BiFeO3-(0.4)PbTiO3 compound oriented in  direction. (i) electron diffraction patterns, and (ii) high-resolution simulated image obtained in  zone axis.
Schematic illustration showing different symmetries of the perovskite structure. (a) cubic (Pm-3m) nonpolar unit cell, (b) tetragonal (P4mm) ( direction) polar unit cell, and (c) rhombohedral (R3m) ( direction) polar unit cell.
Schematic illustration of the weak ferromagnetic arrangement in BiFeO3-based solid solutions. (a) Illustrative cycloidal magnetic structure for the BiFeO3 compound. (b) illustrative breaking of the cycloidal magnetic structure for (1−x)BiFeO3-(x)PbTiO3 solid solutions reached by replacing Fe3+ for Ti4+ ions. MA—magnetic moment of the antiferromagnetic arrangement. MR—resultant magnetic moment of the weak ferromagnetic arrangement.
Schematic illustration showing the behavior of the polarization vector under oscillating electric fields and thermal agitation. (a) When the maximum electric field is applied, there is a positive electric polarization in the sample. (b) When the maximum electric field is applied in the opposite direction, a negative electric polarization emerges. (c) By increasing temperature, the modulus of the electric polarization vector increases until TC. At TC, the thermal agitation contributes to increase the modulus of the electric polarization vector and the average off-center position of the Ti/Fe ion. Above TC, the cubic structure is stabilized and the geometric center of the negative and positive charges is the same.
Rietveld refined structural parameters, at different temperatures, for the (0.75)BiFeO3-(0.25)PbTiO3 compound.
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