| Summary: | 碩士 === 崑山科技大學 === 機械工程研究所 === 101 === The main purpose of this thesis is to develope a new phosphate fluorescent material and to study its characteristics. Potassium phosphate strontium (LiSrPO4) with orthorhombic structure doped with the metal ion Eu3+, Tb3+ or Sm3+ as an activator is studied in this thesis. Additionally, we investigate the effects of the doping concentration and sintering temperature on the microstructural and optical properties of potassium phosphate, strontium (LiSrPO4) by scanning electron microscop (SEM), X-ray diffraction (XRD), photoluminescence spectrum (PL), and Quantum Efficiency(QE).
Results show that the optimum doping concentration of the activator Eu3+ is 7%, and the optimum sintering temperature is 1100 ℃. It is also found that concentration quenching occurred as a result of quadrupole-quadrupole (q-q) interaction according to the Dexter’s theory. When the doping concentration and sintering temperature are above the optimum values, the second phase appeared in LiSrPO4: Eu3+ structure has found. Moreover, the luminescence intensity can be influenced by concentration quench due to the excess doping concentration.
When the Tb3+ activator is doped, the optimum doping concentration is 9%, and the optimum sintering temperature is 1100 ℃. The concentration quenching occurs as a result of dipole-dipole(d-d) interaction according to the Dexter’s theory. From the result of XRD, there is no second phase appeared in LiSrPO4: Tb3+ as the doping concentration of Tb3+ from 5% to 13%. However, as the sintering temperature increases to 1100 ℃, the degradation of the luminescence intensity occurs.
Finally, when the Sm3+ activator is doped, the optimum doping concentration is 0.7%, and the optimum sintering temperature is 1100 ℃. It is found that the concentration quenching occurs as a result of dipole-dipole(d-d) interaction according to the Dexter’s theory. From the result of XRD, there is no second phase appeared in LiSrPO4: Sm3+ as the doping concentration of Sm3+ from 0.5% to 0.13%. However, as the sintering temperature increases to 1100 ℃, the degradation of the luminescence intensity occurs.
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