Luminescence Properties Of Thenardite Activated With Eu And Tb

XinJiang is rich in mineral resources which are distributed extensively. And a lot of minerals have unique physical properties. The natural thenardite from Ai-Ding Salt Lake, Xinjiang, China under 300 nm excitation showed milk-white luminescence, and the PL spectrum consisted of an extremely broad band with a peak located at approximately 509 nm, spreading over a wide range of UV and visible wavelengths. The excitation spectra, obtained by monitoring the luminescence at 530 nm, consisted of a broad band with a peak located at approximately 235 nm and a ?at band spreading over a wide range of UV and visible wavelengths. The PL decay curve of natural thenardite consisted of a fast-decay component with a lifetime of less than 0.1μs and a slow-decay component with a half-decay time of approximately 0.4s. So, we based on the nature thenardite, prepared new phosphors by doped Eu or Tb into thenardite. To reveal the Photoluminescence properties of the new phosphors, it is investigated by X-ray powder diffraction, emission spctra and excitation spectra of photoluminescence, vacuum ultraviolet (VUV) excitation, etc. Through heat treatment and raditate treatment to increase the efficiency of the phosphors. Which are to offer theoretical and technical instructions for exploiting and developing new phospers.Main contents of the thesis are summarized as follows:The photoluminescence (PL) spectra, excitation spectra, and PL decay curves of natural, heat-treated, andγray-irradiated thenardites from Ai-Ding Salt Lake, Xinjiang, China, were studied. The heat treatment of thenardite at 900℃for 20 min reduced the luminescence efficiency to 1/100. Theγray irradiation of thenardite reduced the luminescence efficiency to approximately half.1. Na₂SO₄: Eu phosphors were prepared by heating pure natural thenardite with EuF3 at 900℃for 20 min in air. And their photoluminescence (PL) and excitation spectra of as-prepared andγ-ray-irradiated phosphors were observed at 300 K. The PL spectrum under 394 nm excitation consisted of strong narrow bands with peaks at 579, 592, 616, 652, 697 and 741 nm, assigned to the ⁵D₀-⁷F_J (J= 0, 1, 2,….,5) transitions, respectively, within Eu³⁺. The PL spectrum under 340 nm excitation consisted of a broad Eu²⁺ band with a peak at 435 nm. The excitation spectrum obtained by monitoring the violet luminescence consisted of a weak band with a peak at approximately 261 nm and a broad Eu²⁺ band with a peak at approximately 338 nm. The relative efficiency of the Eu²⁺ band of theγray irradiated phosphor at the exposure of 46kGy increased up to 3.0 times that of the unirradiated phosphor. The enhancement of Eu²⁺ band was ascribed to the conversion of Eu³⁺ to Eu²⁺ in Na2SO4.2. The photoluminescence (PL) spectra of Na2SO4: Tb were investigated under vacuum ultraviolet- ultraviolet (VUV-UV) at room temperature. The excitation spectrum of Na₂SO₄:Tb is consisted of strong bands assigned to the ⁴f_n→⁴f_n-15d transition(186, 190, 218 nm), the host absorption(163, 200, 240 nm), and weak bands assigned to forbidden f-f transitions. In addition, we also found the relative intensity in VUV region was increasing with the increase of Tb³⁺ contents in 0.3 -2.0 mol%.