Systhesis, phase transformation and photoluminescence properties of Eu:La_(1-x)Gd_xVO4 nanofibers by electrospinning method

摘要

One dimensional Eu:La_(1-x)Gd_xVO4 nanofibers were successfully prepared via an electrospinning method. Thermogravimetry and differential scanning calorimeter (TG-DSC), X-ray diffraction, Raman spectroscopy, scanning electron microscopy and photoluminescence were used to characterize the samples. The nanofibers crystallized well below 600 ℃ and with the increase of Gd contents, the nanofibers crystallized in a zircon-type structure. The Raman spectra shifted to higher frequency with the increase of Gd content for zircon Eu:La_(1-x)Gd_xVO4. The peaks of photoluminescence spectra shift towards longer wavelength when Gd replaces La and when x = 0.4, the photoluminescence intensity reaches its maximum value. The band structure and density of states of m-LaVO4, t-LaVO4, t-LaGdVO4 and r-GdVO4 were calculated by local-spin density approximation (LSDA) band theory with Hubbard term of U. The band gap of t-LaGdVO4 is just the average of t-LaVO4 and t-GdVO4. In t-LaGdVO4, La 5p states are highly localized.