In this paper, the relationship between ferroic states and the physicochemical mechanism which governs the (Bi/Pb/La)–O bonds in polycrystalline La doped (0.6)BiFeO₃–(0.4)PbTiO₃ compounds were investigated. An abrupt change in the symmetries of perovskite-structured samples, from tetragonal (P4mm) to rhombohedral (R3c), occurs with the increase of the La concentration, highlighting the diminishment of the hybridization of the (Bi/Pb)–O bonds when La is added into the solid solution, and the emergence of a characteristic morphotropic phase boundary tuned by doping. A maximum remnant polarization (10 μC/cm²) was observed for low La concentrations (where R3c and P4mm phases coexist), while the maximum remnant magnetization (∼75 × 10⁻³ emu/g) was observed for highly La concentrated samples. These results show that ferroelectric and weak-ferromagnetic orders are strongly correlated to the structural arrangement, which in turn are directly related to the chemical A–O and B–O bonds (long-range and short-range forces) and with the chemical characteristics of the elements that fulfills the A site of the perovskite structure.

Biomaterials that effectively act in biological systems, as in treatment and healing of damaged or lost tissues, must be able to mimic the properties of the body’s natural tissues in its various aspects (chemical, physical, mechanical and surface). These characteristics influence cell adhesion and proliferation and are crucial for the success of the treatment for which a biomaterial will be required. In this context, the electrospinning process has gained prominence in obtaining fibers of micro- and nanometric sizes from polymeric solutions aiming to produce scaffolds for tissue engineering. In this manuscript, poly(vinylidene fluoride) (PVDF) was used as a polymeric matrix for the manufacture of piezoelectric scaffolds, exploring the formation of the $\beta$-PVDF piezoelectric phase. Micro- and nanometric hydroxyapatite (HA) particles were incorporated as a dispersed phase in this matrix, aiming to produce multifunctional composite membranes also with bioactive properties. The results show that it is possible to produce membranes containing micro- and nanofibers of the composite by the electrospinning process. The HA particles show good dispersion in the polymer matrix and predominance of $\beta$-PVDF phase. Also, the composite showed apatite growth on its surface after 21 days of immersion in simulated body fluid (SBF). Tests performed on human fibroblasts culture revealed that the electrospun membranes have low cytotoxicity attesting that the composite shows great potential to be used in biomedical applications as bone substitutions and wound healing.

In this review, the state of the art in understanding the structural phase relations in perovskite-structured BiFeO₃-based polycrystalline solid solutions is presented and discussed. Issues about the close relation between the structural phase and overall physical properties of the reviewed systems are pointed out and discussed. It is shown that, by adjusting the structural symmetric arrangement, the ferroelectric and magnetic properties of BiFeO₃-based polycrystalline solid solutions can be tuned to find specific multifunctional applications. However, an intrinsic mechanism linking structural arrangement and physical properties cannot be identified, revealing that this subject still deserves further discussion and investigation.

In this work, we analyze the defect and antidefect distribution in the nematic calamitic phase of a lyotropic liquid crystal [the ternary mixture formed by potassium laurate (KL), decanol (DeOH), and water]. We obtain defects with wedge disclinations of strength $\pm 1∕2$, and the scaling exponent determined by the defect-antidefect correlation was $0.29\pm 0.07$. This value is in good agreement with the theoretical value of $1∕4$ obtained by the Kibble mechanism. The constant of the scaling relation of the defect and antidefect distribution is also discussed. We compare our results with the values obtained by Digal et al. [Phys. Rev. Lett. 83, 5030 (1999)] who used a thermotropic liquid crystal.