Systhesis, phase transformation and photoluminescence properties of Eu:La1−xGdxVO4 nanofibers by electrospinning method

Abstract

One dimensional Eu:La_1−xGd_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 °C 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−xGd_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 t-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.