X.X. Wang

Electromechanical and ferroelectric properties of (Bi1∕2Na1∕2)TiO3–(Bi1∕2K1∕2)TiO3–BaTiO3 lead-free piezoelectric ceramics

Lead-free piezoelectric ceramics (0.95−x)(Bi1∕2Na1∕2)TiO3–x(Bi1∕2K1∕2)TiO3–0.05BaTiO3 (abbreviated as BNT–BKT–BT100x, with x ranged from 0 to 20mol%) have been studied. Effects of amount of BKT on the electrical properties and crystal structure were examined. BNT–BKT–BT5 ceramics give good performances with piezoelectric constant d33=148pC∕N, electromechanical coupling factor kp=34%, kt=49.2%, free permittivity e33T∕e0=700, and dissipation factor tanδ=2% at 1kHz. Accordingly, the sample shows larger remanent polarization and lower coercive field than 0.95BNT–0.05BT ceramics. X-ray diffraction analysis shows that incorporated BKT diffuses into the BNT–BT lattice to form a solid solution during sintering, but changes the crystal structure from rhombohedral to tetragonal symmetry at higher BKT amounts.

Dielectric behavior and microstructure of (Bi1∕2Na1∕2)TiO3–(Bi1∕2K1∕2)TiO3–BaTiO3 lead-free piezoelectric ceramics

(0.95−x)(Bi1∕2Na1∕2)TiO3–x(Bi1∕2K1∕2)TiO3–0.05BaTiO3 lead-free piezoelectric ceramics (abbreviated as BNT–BKT–BT100x with x varying from 0 to 20 mol %) are prepared by a solid-state reaction process. Variation of the dielectric properties and microstructure of BNT–BKT–BT100x ceramics with BKT content is studied. The results indicate that the relative permittivity er and loss tangent tanδ vary with the BKT amount. Scanning electron microscope observation also indicates that BKT in high amount affects the microstructure. X-ray diffraction analysis shows that the incorporated BKT diffuses into the BNT–BT lattice to form a solid solution during sintering.

0.75(Bi1/2Na1/2)TiO3-0.20(Bi1/2K1/2)TiO3-0.05BaTiO3 Lead-Free Ceramics with Addition of CeO2

Lead-free piezoelectric 0.75(Bi 1/2 Na 1/2 )TiO 3 -0.20(Bi 1/2 K 1/2 )TiO 3 -0.05BaTiO 3 ceramics(abbreviated as BNKBT-20) with addition of 0.2, 0.4, 0.6 and 0.8 wt% of CeO 2 , respectively, were prepared by a conventional mixed oxide method. The addition of CeO 2 can reduce the dissipation factor and enhance the mechanical quality factor significantly. The composition with 0.4 wt% CeO 2 has a piezoelectric d 33 constant of 129 × 10− 12 C/N and a relatively low dissipation factor (tan δ = 1.8%) at 1 kHz which shows a 50% reduction in the dissipation factor when compared with BNKBT-20 before doping (tan δ = 3.74%).

ZnO nanorod/nickel phthalocyanine hierarchical hetero-nanostructures with superior visible light photocatalytic properties assisted by H2O2

Needle-like ZnO nanorod (ZnO-NR)/2,9,16,23-tetra-phenoxy nickel phthalocyanine (TPNiPc) nanofiber hierarchical hetero-nanostructures have been successfully designed and constructed via a two-step hydrothermal approach on zinc foil. The as-prepared ZnO-NR/TPNiPc hierarchical hetero-nanostructure exhibited superior photocatalytic activities in degradation of Rhodamine B assisted by H2O2 under visible light irradiation with excellent efficiency, recyclability and stability. The intermolecular electron transfer in the process of photocatalysis was further confirmed by the enhanced photocurrent. This method offers a simple, economical, and convenient way to obtain a highly efficient visible-light photocatalyst based on ZnO, showing great industrial application potential in eliminating the organic pollutants from wastewater.

H2O-induced degradation in TiO2-based ceramic capacitors

Abstract H 2 O-induced degradation in TiO 2 -based ceramic capacitors (rutile-based ceramic capacitor) was studied by means of the electrolysis of water. In the test, the ceramic capacitors were placed in a 0.01 M NaOH solution and a small dc voltage was applied to evolve hydrogen onto their silver electrodes. The samples treated by electrolysis of water showed obvious degradation as their permittivity decreased and their dielectric loss increased significantly. I – V measurements indicated that the resistance decreased greatly in the degraded samples. The decrease in resistance could be ascribed to the generation of charge carriers due to the reduction reaction of atomic hydrogen from the electrolysis of water. These results suggested that the reduction reaction of atomic hydrogen at ambient temperature was a cause of the degradation for the rutile ceramic capacitors.