We report on the reduction of band gap in Bi0.5(Na0.82-xLixK0.18)0.5(Ti0.95Sn0.05)O3 from 2.99 eV to 2.84 eV due to the substitutions of Li+ ions to Na+ sites. In addition, the lithium substitution samples exhibit an increasing of the maximal polarizations from 21.8 to 25.7 μC/cm2. The polarization enhancement of ferroelectric and reduction of the band gaps are strongly related to the Li substitution concentration as evaluated via the electronegative between A-site and oxygen and tolerance factor. The results are promising for photovoltaic and photocatalytic applications.
The lead-free piezoelectric ceramics display good piezoelectric properties which are comparable with Pb(Zr,Ti)O3(PZT) and these materials overcome the hazard to the environment and human health. The Bi0.5(Na,K)0.5TiO3(BNKT) is rapidly developed because of good piezoelectric, ferroelectric, and dielectric properties compared to PZT. The origin of giant strain of BNKT piezoelectric materials was found at morphotropic phase boundary due to crystal change from tetragonal to orthorhombic and/or precipitation of cubic phases, in addition to domain switching mechanism. The dopants or secondary phases withABO3structure as solid solution are expected to change the crystal structure and create the vacancies which results in enhancement of the piezoelectric properties. In this work, we reviewed the current development of BNKT by dopants and secondary phase as solid solution. Our discussion will focus on role of dopants and secondary phase to piezoelectric properties of BNKT. This result will open the direction to control the properties of lead-free piezoelectric materials.
A miniaturized highly sensitive single-chip multichannel quartz-crystal microbalance prepared by deep reactive ion etching is presented. In the present work, quartz resonators in a single-chip with the diameters in the range 0.05–1.0 mm and thicknesses in the range 18–82 μm were fabricated. The conductance measurements carried out on the resonators showed that the Q factor is inversely proportional to resonator thickness. The Q-factor value as high as ∼30 000 has been observed in case of a 94 MHz resonator whose diameter is 1 mm and the thickness 17.8 μm. The Q factor of a resonator of very small diameter (0.1 mm) reached the value 5700.
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