Energy Transfer And Temperature Effect In Rare Earth Ions (Eu³⁺?Sm³⁺?Er³⁺?Tm³⁺?Yb³⁺) Doped Luminescence Materials

Rare earth doped luminescent materials have exhibited wide applications in the fields such as lighting, displays, lasers, Anti-counterfeiting, optical fiber communication and biomedicine ect, and become a research hot spot for multi-cross-discipline. So far white light-emitting diode ?LED? has been widely used in daily life lighting, as well as in other special fields, such as port lighting, traffic lights, vehicles lights ?cars, trains, boats, airplanes cubicle illumination?. In the field of transport, new lighting and laser materials are widely used in all kinds of vehicles. In the future, white LED can also be used in the ocean platform lighting, as well as special lighting of the military. White LED employed in the vehicles of ships, naval vessels and aircraft can reduce the consumption of energy and improve the self-supportability of vehicles efficiently.Energy transfer is a physical phenomenon, which generally exists in luminescent centers. It has positive and negitive influences on the performance of the luminescent materials. In practical applications, the spectroscopic properties of rare earth doped luminescent materials can be controlled by energy transfer. In addition, energy absorbed by the rare earth ion cannot be totally used for emitting light, but partly converted into thermal vibration energy of lattices by nonradiative transitions, which cause the increase of material temperature and affect the luminescence properties of the materials. Moreover, temperature effect on the spectral properties in rare earth ions doped luminescence materials is also the fundamental physical problem that people concern about. This thesis is focused on the energy transfer and temperature effect of rare earth ions doped luminescence materials. The obtained main results are as follows.?1? KLa?MoO₄?₂:Eu³⁺ red phosphors were successfully synthesized by a conventional high-temperature solid state reaction. The effects of calcination temperature, Eu³⁺ doping concentration on crystal structure and luminescence properties of the sample were discussed. The excitation spectra indicated that the energy can be transfer effectively from host ?MoO2-? to luminescence centre (Eu³⁺).The concentration quenching between Eu³⁺ ions was studied based on the Van Uitert's model. It was found that electric dipole-dipole interaction is responsible for the fluorescence quenching of 5D2 and 5D1 levels, but exchange interaction is in charge of 5Do fluorescence quenching.The color coordinates of all the samples with various Eu³⁺doping concentrations were studied. It was found that the 30% Eu³⁺ doped sample showed color coordinates ?0.650, 0.333?. Temperature quenching phenomenon was also studied by Arrhenius's equation and the main mechanism of temperature quenching of 5D0 fluorescence was crossover process. Judd-Ofelt parameters for Eu³⁺ in KLa?MoO₄?₂ phosphors were calculated by emission spectra and decay curve.?2? KLa ?MoO₄?₂:Eu³⁺/Sm³⁺ red phosphors were successfully synthesized via a conventional high-temperature solid state reaction, and the energy transfer behaviors between Eu³⁺ and Sm³⁺ were discussed. When the Sm³⁺concentration was low, the emission intensities under 277 and 395 nm excitations almost did not change with Sm³⁺ concentration, but effective luminescent enhancement was observed with increasing the Sm³⁺ concentration under 404 nm excitation. However, Sm³⁺ doping quenched the emission of Eu³⁺ when the Sm³⁺ doping concentration was higher. The electric multipole interaction and exchange interaction models were adopted to explore physical nature for the energy transfer mechanism, and it was discovered that the exchange interaction between Sm³⁺ and Eu³⁺ was confirmed to be the right mechanism.?3? Sm³⁺ doped silicate glasses were successfully prepared via a conventional melt-quenching and annealing technique. Optical transition properties of Sm³⁺ in the studied silicate glass were calculated from the absorption spectrum in the framework of Judd-Ofelt theory. The concentration quenching mechanism between Sm³⁺ ions was studied based on the Van Uitert's and Inokuti-Hirayama's model, and the results revealed the main reason for concentration quenching was nonradiative energy transfer through cross-relaxation mechanism due to dipole-dipole interaction between rare earth ions. The fluorescence temperature quenching behavior of 4G5/2 level was analyzed based on the dependence of fluorescence intensity on temperature, and results revealed that quenching behavior of 4G5/2 could be ascribed to the crossover process and the activation energy was calculated to be 0.40 eV.?4? Eu³⁺ and Sm³⁺/Eu³⁺ doped borate glasses were successfully synthesized via a conventional melt-quenching and annealing technique. Optical transition properties of Eu³⁺in the studied borate glass were derived from the absorption spectrum in the framework of Judd-Ofelt theory. Electron-phonon interaction in the studied borate glass was discussed by Eu³⁺ probe, and that the Huang-Rhys factor was achieved to be 5=0.010, the phonon energy is 1349.6 cm"1. Energy transfer behaviors between Eu³⁺ and Sm³⁺were discussed by fluorescence spectra and decay curve. When the Sm³⁺ concentration was low, the emission intensity of 5D0 can be increased by energy transfer from Sm34 to Eu³⁺. However, when the Sm³⁺ doping concentration was higher, the emission intensity of 5D0 would be quenched via energy transfer from Eu³⁺ to Sm³⁺.?5? Er³⁺/Yb³⁺ codoped GdNbO4 phosphors with various concentrations of Er³⁺ or Yb³⁺ were successfully obtained via a conventional high-temperature solid state reaction. Under excitation at 980 nm, the effect of the Er³⁺ and Yb³⁺ doping concentration on the upconversion intensity was investigated. It was found that the optimal concentration for Er³⁺ and Yb³⁺ was 7 mol% and 10 mol%, respectively. Temperature effect of GdNbO4:10%Yb³⁺, 7%Er³⁺ phosphors was also discussed under 980 nm excitation. The experimental results indicated that the sample was exhibited excellent optical temperature sensing properties. The temperature quenching model of Er³⁺ green emission was established, and successfully explained dependence of the fluorescence intensity of 4S3/3?4I15/2,2H11/2?4I15/2 on temperature.?6? Tm³⁺/Yb³⁺ codoped oxyfluoride tellurite glasses were successfully produced via a conventional melt-quenching and annealing technique. Optical transition properties of Tm³⁺ in the studied oxyfluoride tellurite glasses were calculated from the absorption spectrum based on Judd-Ofelt theory. Under near infrared 980 nm excitation, the effect of the Tm³⁺ doping concentration on the upconversion intensity was investigated. It was found that the optimal Tm³⁺ concentration for achieving maximum upconversion emission intensity was 0.1%. Under near infrared 980 nm excitation, the optical temperature sensing properties were investigated by using the thermal coupling 3F2,3 and 3H4 levels of Tm³⁺.