Effect of Internal Bias Field on Poling Behavior in Mn-Doped Pb(Mg1/3Nb2/3)O3-29 mol%PbTiO3 Single Crystal

Electrical poling is a crucial step to convert ferroelectrics to piezoelectrics. Nevertheless, no systematic investigation on the effect of poling has been reported. Given that the poling involves an alignment of spontaneous polarization,the condition for poling should be different when a material has an internal bias field that influences the domain stability. Here, we present the effect of poling profile on the dielectric and piezoelectric properties in Mn-doped Pb(Mg1/3Nb2/3)O3-29 mol%PbTiO3 single crystal with an internal bias field. We showed that both the dielectric permittivity and the piezoelectric coefficient were further enhanced when the poling procedure ends with a field application along the opposite direction to the internal bias field. We expect that the current finding would give a clue to understanding the true mechanism for the electrical poling

Dimeric configuration of SeqA protein bound to a pair of hemi-methylated GATC sequences

The binding of SeqA protein to hemi-methylated GATC sequences (hemi-sites) regulates chromosome initiation and the segregation of replicated chromosome in Escherichia coli. We have used atomic force microscopy to examine the architecture of SeqA and the mode of binding of one molecule of SeqA to a pair of hemi-sites in aqueous solution. SeqA has a bipartite structure composed of a large and a small lobe. Upon binding of a SeqA molecule to a pair of hemi-sites, the larger lobe becomes visibly separated into two DNA binding domains, each of which binds to one hemi-site. The two DNA binding domains are held together by association between the two multimerization domains that make up the smaller lobe. The binding of each DNA binding domain to a hemi-site leads to bending of the bound DNA inwards toward the bound protein. In this way, SeqA adopts a dimeric configuration when bound to a pair of hemi-sites. Mutational analysis of the multimerization domain indicates that, in addition to multimerization of SeqA polypeptides, this domain contributes to the ability of SeqA to bind to a pair of hemi-sites and to its cooperative behavior

Solid state crystal growth of single crystals of 0.75(Na1/2Bi1/2)TiO3-0.25SrTiO(3) and their characteristic electrical properties

Ceramics of composition 0.75(Na1/2Bi1/2)TiO3-0.25SrTiO(3) (NBT-25ST) show a giant electric field-induced strain, making them attractive for actuator applications. Single crystals generally have improved piezoelectric properties over their ceramic counterparts, but the electrical properties of NBT-25ST single crystals have not yet been studied. In this work, NBT-25ST single crystals are grown by the solid state crystal growth technique and their electrical properties measured for the first time. The single crystals show relaxor ferroelectric behavior typical of an NBT-type material. The ferroelectric and inverse piezoelectric properties depend strongly on crystallographic orientation, with superior properties in the (001) orientation. The inverse piezoelectric properties of the (001)-oriented NBT-25ST single crystal are superior to those of an NBT-25ST ceramic (S-max/E-max = 1042 pm/V vs. 739 pm/V)

Mechanism for the Electromechanical Properties of Relaxor-PbTiO3 Piezoelectric Single Crystals

Department of Materials Science and Engineeringclos

Strategies of A Potential Importance, Making Lead-Free Piezoceramics Truly Alternative to PZTs

Active search for lead-free piezoceramics over the last decade has harvested a considerable amount of achievements both in theory and in practice. Few would deny that those achievements are highly beneficial, but agree that this quest of developing the lead-free piezoceramics in replace for PZTs is successfully completed. Nevertheless, few would clearly state where this quest should be directed in our next move. A source of this uncertainty may originate from the fact that it is still not clear how good is good enough to beat PZTs. In this short review, we analyzed the existing literature data to clearly locate the current state of the art of lead-free piezoceramics in comparison to PZT-based piezoceramics. Four strategies of a potential importance were suggested and discussed to help researchers plan and design their future research on lead-free piezoceramics with a recently reported exemplary work