Luminescence Properties Of Thenardite From Xinjiang Activated With Tm And Dy

The natural thenardite from Ai-Ding Salt Lake, Xinjiang, China under 300nm 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 flat 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.This thesis based on study of natural thenardite consists of two parts:(1) preparation and photoluminescence properties of thenardite activated with Tm³⁺ under vacuum ultraviolet excitation,and (2) preparation and photoluminescence properties of thenardite activated with Dy³⁺ under vacuum ultraviolet excitation.1. Na₂SO₄:Tm³⁺ phosphors were prepared by heating pure natural thenardite with TmF3 at 900℃for 20 min in air. And their photoluminescence (PL) spectra were also investigated under vacuum ultraviolet-ultraviolet (VUV-UV) at room temperature. Narrow bands observed in emission spectra were well identified with the electronic transitions within the 4f12 configurations of Tm³⁺ , and the excitation spectrum is consisted of strong bands assigned to the 4f12→4f11 5d transition at 183nm, the O2-- Tm³⁺charge transfer band at170nm and weak bands assigned to host absorption(130, 223, 258 nm). In addition, we also found the relative intensity in VUV region was increasing with the increase of Tm³⁺ contents in 2-8mg. Content in 8-16mg occur concentration quenching.2. Na₂SO₄:Dy³⁺ phosphors were prepared by heating pure natural thenardite(Na₂SO₄) with DyF3 at 900℃for 25 min in air. Studied the luminescence properties of Na₂SO₄:Dy³⁺ by synchrotron radiation. And their photoluminescence (PL) spectra were also investigated under vacuum ultraviolet-ultraviolet (VUV-UV) at room temperature. According to the Emission spectra, the yellow-blue ratio (Y/B) is different under different concentrations of Dy³⁺ and position of excitation. And the excitation spectrum is consisted of strong bands assigned to the 4f9→4f8 5d transition at 172nm, the O^2-- Tm³⁺charge transfer band at 165nm and weak bands assigned to host absorption(138, 245nm) and the ⁶H_15/2→⁴D_7/2,⁶H_15/2→⁶P_3/2,⁶H_15/2→⁶P_7/2 transition at 299nm,325nm,351nm.