Ternary solid solutions of BiFeO3, GdFeO3 and BaTiO3 have been prepared by solid-state reaction method. Dielectric properties of these ceramics have been characterized in the temperature range ...between room temperature and 673 K and magnetic properties between 5 K and 300 K. For the understanding of the multiferroic property, the relation between the crystal structures, magnetic transition and ferroelectric transitions with increasing temperature have been analyzed. All ceramic samples show single perovskite phase. When Ba content exceeds 0.2 wt%, the sintering ability is weakened and the phase structure of Bi1-x-yGdxBayFe1-yTiyO3 (with x = 0.2 and y = 0.1, 0.2, 0.3, 0.4, 0.5) solid solution changes from rhombohedral to tetragonal phase. The maximum ferroelectric transition temperature (Te of this system was in the range 154–165°C with the dielectric constant peak of 6000 for y = 0.5 at 100 kHz. Well-saturated piezoresponse hysteresis loops were observed for all compositions indicating room temperature ferroelectricity. With increasing Ba content (up to 0.3 wt%) the remanent magnetization Mr increased and the coercive magnetic field decreased.
Sol-gel processing parameters of Pb
0.99Zr
0.55Sn
0.37 Ti
0.06Nb
0.02O
3 thin films were studied. Effects of H
2O, HNO
3 and formamide additives on solution gelation and film properties were ...investigated. Thin films were prepared on
Ti
Pt
and
Ta
Pt
metallized Si substrates. Film microstructures were characterized using SEM, TEM/EDS and XPS. Film microstructures typically contained ‘rosette’ structures. Strain response of the films under applied electric fields was measured using a double beam interferometer. A piezoelectric double loop was obtained with an effective d
33 as high as 60 pm V
−1, being strongly AC field dependent. Double P-E hysteresis loops with maximum polarizations of 30 μC cm
−3 were measured. Field-induced antiferroelectric to ferroelectric phase switching was observed at 110 kV cm
−1 and reverse switching at 74 kV cm
−1. Films prepared on
Ti
Pt
yielded better electrical properties. This may be attributed to a change in nucleation/ crystallization mechanism due to Pb diffusion through the Pt during film annealing.
Piezoelectricity is one of the common ferroelectric material properties, along with pyroelectricity, optical birefringence phenomena, etc. There has been widespread observation of piezoelectric and ...ferroelectric phenomena in many biological systems and molecules, and these are referred to as biopiezoelectricity and bioferroelectricity. Investigations have been made of these properties in biological and organic macromolecular systems on the nanoscale, by techniques such as atomic force microscopy (AFM) and piezoresponse force microscopy (PFM). This chapter presents a short overview of the main issues of piezoelectricity and ferroelectricity, and their manifestation in organic and biological objects, materials and molecular systems. As a showcase of novel biopiezomaterials, the investigation of diphenylalanine (FF) peptide nanotubes (PNTs) is described in more detail. FF PNTs present a unique class of self-assembled functional biomaterials, owing to a wide range of useful properties, including nanostructural variability, mechanical rigidity and chemical stability. The discovery of strong piezoactivity and polarization in aromatic dipeptides ACS Nano 4, 610, 2010 opened up a new perspective for their use as nanoactuators, nanomotors and molecular machines as well for possible biomedical applications.
