Lead‐free (1−x/2) K0.5Na0.5Nb0.95Ta0.05O3–x/2Fe2O3 piezoelectric ceramics (x=0, 0.2, 0.4, 0.6, 0.8, 1.0, 2.0, and 3.0 mol%) have been prepared by conventional ceramic sintering process. The effects of doped iron element on the structure, dielectric, and piezoelectric properties were investigated. The introduction of ferric oxide (Fe2O3) was effective in improving the piezoelectric properties and sintering characteristics by refining grain size, reducing micropores and increasing the density of the ceramics. The bulk density reached the steady value of around 4.52 g/cm3, about 96% of the theoretical value. The samples with x=0.4 mol% show the maximum values of the piezoelectric coefficient (d33=130 pC/N) and the planar electromechanical coupling coefficient (kP=37.2%), which is significantly enhanced compared with the undoped samples. K+ and Na+ vacancies and charge compensation of the diffused Fe ions in the ceramics induce domain wall motions, which might be responsible for the improvement of structure and electrical properties. Fe2O3 was considered to be a “soft” addition for alkali niobate piezoelectric ceramics at low doping concentration.

Er(3+) green upconversion (UC) emission corresponding to the transition of (4)S(3/2) ((2)H(11/2))-->(4)I(15/2) is enhanced in a Er/Dy-codoped LiNbO(3) crystal compared with Er-doped LiNbO(3) under 800 nm femtosecond-laser excitation at room temperature. The upconversion mechanisms are proposed based on spectral, kinetic, and pump-power dependence analyses. The energy-transfer efficiency from Dy(3+)((4)F(9/2)) to Er(3+)((4)F(7/2)) is 33%, which results in the enhancement of green UC emission. This energy transfer is advantageous for the Er(3+) UC emission sensitized by Dy(3+), especially in a low-phonon-energy host matrix.

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The properties of inorganic nanoparticles/polymer composites depend on the dispersivity of nanoparticles in a polymer matrix. The effect of surface modification on the dispersivity of ZnO nanoparticles in a polyurethane (PU) resin matrix was investigated. The nanocomposites were characterized by scanning electron microscopy (SEM), thermogravimetric analysis, and X‐ray diffraction. The scanning electron micrographs show that ZnO nanoparticles (CDI–SA–APS–ZnO), which were modified by aminopropyltriethoxysilane (APS) and activated stearic acid (SA) by N,N′‐carbonyldiimidazole (CDI), can be homogeneously dispersed and had been encapsulated in the PU phase. The interfacial compatibility between ZnO nanoparticles and PU matrix was significantly improved by hydrophobically modifying ZnO nanoparticles with APS and SA. The tensile strength and elongation at break of PU/CDI–SA–APS–ZnO nanocomposites increased by 82 and 64% respectively, compared with the pure PU material. The thermal stability and ultraviolet‐shielding properties were also improved by incorporating ZnO nanoparticles into the PU matrix. POLYM. COMPOS., 35:237–244, 2014. © 2013 Society of Plastics Engineers

Leakage current characteristics of (Bi0.86Pr0.14)(Fe0.95Mn0.05)O3 (BPFMO) thin films are studied at various temperatures from 293 down to 93 K. Space charge limited current and Poole–Frenkel (PF) emission are found to be the dominant mechanism in the low and the high electric fields, respectively. The trap ionization energy at zero-field in BPFMO films is deduced to be around 0.29 eV, which indicates the existence of shallow traps. A negative differential resistivity behavior is observed before the onset of PF emission at 93 K, which is discussed in terms of the competition between electron trapping and field-assisted thermal emission.