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Hydrothermal synthesis of rare earth doped NaYF_4-conversion and down conversion Luminescence Properties
Time:06/07/2011

  Hydrothermal synthesis of rare earth doped NaYF_4-conversion and down conversion Luminescence Properties

  Phosphor Doped NaYF4 whispered the energy of the high reflectivity, optical transparency and excellent light performance advantages in optical light, near infrared detection and bio-calibration, the potential application areas.This paper, through a simple hydrothermal method NaYF4 of rare earth doped phosphor, the phosphor is designed to study the structure and properties of NaYF4 to explain the related mechanism of the conversion and down conversion, and to explore its potential applications in various fields.

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  The first chapter discusses the process of development of rare earth doped phosphors, highlighted the plight of rare earth doped phosphor-conversion and down-conversion luminescence.

  The second chapter discusses the relevant theoretical and experimental methods.

  Chapter prepared by hydrothermal method with good performance on the conversion Er ~ (3 +) / Yb ~ (3 +) co-doped LiYF4, NaYF4, BaYF5 upconversion luminescence materials.X-ray diffraction analysis and scanning electron microscope analysis of the resultant composition and morphology, and study the Er ~ (3 +) / Yb ~ (3 +) ions on the matrix of the three fluoride upconversion mechanism.980 nm light-emitting diode (LD) excitation sample, when the Er ~ (3 +) ion concentration is fixed at 2 mol.%, Three matrix Yb ~ (3 +) ion concentration were 10,20,20 mol.%, the corresponding conversion of red / green emission is strongest.Spectrum in the same test conditions, the performance of three different matrix splitting mode, and NaYF4: Er ~ (3 +), Yb ~ (3 +) showed the strongest up-conversion properties, LiYF4: Er ~ (3+), Yb ~ (3 +) have an advantage in the green emission, while the BaYF5: Er ~ (3 +), Yb ~ (3 +) showed weak up-conversion performance.On this basis, the study NaYF4: Er ~ (3 +), Yb ~ (3 +) spectral characteristics of the next conversion.448 nm excitation, the near-infrared luminescence from Er ~ (3 +) ions 4F7 / 2 level of the cascade emission: Er ~ (3 +): 4F7 / 2 + Yb ~ (3 +): 2F7 / 2 → Er~ (3 +): 4I11 / 2 + Yb ~ (3 +): 2F5 / 2; Er ~ (3 +): 4I11 / 2 + Yb ~ (3 +): 2F7 / 2 → Er ~ (3 +):4I15 / 2 + Yb ~ (3 +): 2F5 / 2 or Er ~ (3 +): 4I11 / 2 → Er ~ (3 +): 4I15 / 2, the 4F7 / 2 level through the intermediate level easy 2H11 /2 non-radiative relaxation to the 4S3 / 2, so the conversion efficiency is low.In the 377 nm excitation, Er ~ (3 +) ions and Yb ~ (3 +) ions between the cross-relaxation: Er ~ (3 +): 4G11 / 2 + Yb ~ (3 +): 2F7 / 2 →Er ~ (3 +): 4F9 / 2 + Yb ~ (3 +): 2F5 / 2, so that 653 nm red light intensity with Yb ~ (3 +) ion concentration increased with the increase, the system the way to the formation of quantum cutting 653nm and 1000 nm photons of red light near infrared photons.

  The fourth chapter discusses the NaYF4: Ho ~ (3 +), Yb ~ (3 +) system on the conversion and down-conversion performance.In the 980 nm LD excitation, through the Yb ~ (3 +) ions in the sensitizing effect, at 483 nm, 540 nm, 644 nm and 749 nm observed at the strong up-conversion visible light, corresponding to Ho ~ (3 +) ionsthe 5F3 → 5I8, 5S2 → 5I8, 5F5 → 5I8, and 5S2 → 5I7 transition.Luminous intensity with Yb ~ (3 +) ion concentration increased sharply increased in the 30 mol.% Less than the phenomenon of concentration quenching does not appear.In the 448 nm excitation, NaY0.99F4: Ho0.01 than visible light emission in addition, also at 966 nm and 1012 nm are also near-infrared light, corresponding to 5F5 → 5I7, and 5S2 → 5I6 transition.Yb ~ (3 +) ions after the entry of visible light intensity decreased significantly, while the near-infrared light intensity increased significantly, resulting in a Yb ~ (3 +) ion 978 nm of the characteristic emission, which is by Ho ~ (3 +): 5S2+ Yb ~ (3 +): 2F7 / 2 → Ho ~ (3 +): 5I6 + Yb ~ (3 +): 2F5 / 2, and Ho ~ (3 +): 5F5 + Yb ~ (3 +): 2F7 /2 → Ho ~ (3 +): 5I7 + Yb ~ (3 +): 2F5 / 2 caused by the two cross-relaxation process.

  The fifth chapter NaYF4: Pr ~ (3 +), Yb ~ (3 +) system, found in near-infrared luminescence.Blu-ray excitation at 443 nm (Pr ~ (3 +): 3H4 → 3P2), Pr33P0 → 3Hi (i = 5, 6), 3Fj (+ ion in the visible region of the emission peak at 482 nm, 522 nm, 606 nm, 640 nm, 688 nm and 721 nm corresponding to Pr ~ (3 +) ions in the 3P0 → 3H4, j = 2, 3, 4) the level transition.Since Pr ~ (3 +) / Yb ~ (3 +) energy transfer between ions, through the cooperation of converting a way that Yb ~ (3 +) ions near infrared emission 977 nm Yb ~ (3 +): 2F5/ 2 → 2F7 / 2.By adjusting the Yb ~ (3 +) doping concentration, the optical properties of system and mechanism.When the Yb ~ (3 +) ion concentration was 2mol.%, The maximum quantum efficiency of 133.6%.