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Abstract: The phase formation, morphology and luminescent properties of ZnNb2O6 nanocrystals by the sol–gel method were investigated at a lower temperature than that of the traditional solid-state reaction method. The products were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), photoluminescence spectroscopy (PL) and absorption spectra. The activation energy of ZnNb2O6 grain growth is obtained about 18.4kJ/mol. The diameters of the nanocrystals are in the range of 20–40nm. The PL spectra excited at 276nm have a broad and strong blue emission band maximum at 450nm, corresponding to the self-activated luminescence of the niobate octahedra group [NbO6]7−. The optical absorption spectrum of the sample at a calcination temperature of 800°C has a band gap energy of 3.68eV. [ABSTRACT FROM AUTHOR]

Abstract: Pyrochlores with composition (NaBi)(NbCr)O6 were sintered in the temperature range of 1100–1250 °C. Dielectric properties of the ceramics were investigated in a wide range of temperatures of −15 to 200 °C and frequencies of 1–800 kHz. The suitable sintering temperatures for (NaBi)(NbCr)O6 ceramics are suggested from 1150 to 1200 °C. The dielectric constant behavior reflects, in our opinion, the formation of the space charge and the orientational polarization. The pyrochlores have convex resistivity-temperature characteristics around the transition point, and exhibit the negative temperature coefficient of resistance characteristics. The activation energies of conductivity of samples were obtained at various sintering temperatures. [Copyright &y& Elsevier]

Abstract: Photoluminescence characterization of LiZnVO4 oxides by the vibrating milled solid-state reaction was investigated in this work. The products were characterized by X-ray diffraction, scanning electron microscopy, photoluminescence spectroscopy and absorption spectra. The excitation wavelengths associated with charge transfer bands of [VO4]3− are located at 355nm. The photoluminescence results reveal that the sample prepared at 500°C exhibits a broad and strong bluish green emission peaks at about 526nm compared with other samples. Furthermore, the visible light absorption edge of the LiZnVO4 annealed at 500°C was located at 413nm, which corresponded to band-gap energy of 3.0eV. [Copyright &y& Elsevier]