G. S. Dias

Structural phase relations in perovskite-structured BiFeO 3 based multiferroic compounds

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.

Structural Refinement and Ferroic Properties in BiFeO3–Based Compounds

Nanostructured BiFeO3 - XTiO3 (X = Ba or Pb) multiferroic ceramics were processed by mechanosynthesis and a detailed structural study was conducted through Rietveld refinement of X-ray diffraction patterns. It was found that the structural and ferroic properties have been improved by the formation of double-phased compounds in both cases. In fact, ferroelectric investigations indicated a structurally tuned ferroic state, where the ferroelectricity is strongly affected by the coexistence of two distinct symmetries in BiFeO3 -based solid solutions.

Highly resistive fast-sintered BiFeO3 ceramics

ABSTRACT This contribution presents an alternative synthesis route to produce highly resistive BiFeO3 multiferroic samples. The use of a fast sintering process followed by quenching to room temperature resulted in ceramic bulks with a resistance higher than 1012 Ohm.m at room temperature. In addition, anomalies found in the dielectric and resistivity characterization indicated the presence of magnetoelectric coupling in the synthesized BiFeO3 sample.

Photoacoustic methods for in vitro study of kinetics progesterone release from the biodegradation of polyhydroxybutyrate/polycaprolactone used as intravaginal devices

Intravaginal devices composed of polyhydroxybutyrate/polycaprolactone blends incorporating progesterone were used over eight days in crossbred cow ovariectomized, and then analyzed with photoacoustic methods, measuring the absorption spectra, thermal diffusivity, and inspecting its degradation by means of scanning electron microscopy. The characteristic time found for progesterone release was TR ∼ 53 h, and the typical time found for biodegradation was TB ∼ 30 h. Morphological analysis complements the study showing that release of progesterone and biodegradation of the blend occurs on sample surface.