TAILIEUCHUNG - Optical properties of Eu3+ ions in LaF3 nanocrystals
LaF3 nanocrystals doped with different concentrations of Eu3+ ions were synthesized by hydrothermal method. The XRD, luminescence and excitation spectra have been studied at room temperature. The ratio of the 5D0→7 F2 electric dipole transition intensity to the 5D0→7 F1 magnetic dipole transition intensity (R) was used to evaluate the asymmetry of Eu3+ site. JuddOfelt parameters were calculated from emission spectra and were used to predict the radiative properties of 5D0→7 FJ transitions also the lifetime of 5D0 level. | Journal of Science and Technology 54 (1A) (2016) 88-95 OPTICAL PROPERTIES OF Eu3+ IONS IN LaF3 NANOCRYSTALS Hoang Manh Ha1,*, Tran Thi Quynh Hoa2, Nguyen Ngoc Long3, Le Van Vu3, Phan Van Do4 1Hanoi 2National Architectural University, Km 10 Nguyen Trai, Thanh Xuan, Hanoi University of Civil Engineering, 55 Giai Phong, Hai Ba Trung, Hanoi 3Hanoi University of Science, 334 Nguyen Trai, Thanh Xuan, Hanoi 4Thuy Loi University, 175 Tay Son, Dong Da, Hanoi * Email: hahm1982@ Received: 30 August 2015; Accepted for publication: 25 October 2015 ABSTRACT LaF3 nanocrystals doped with different concentrations of Eu3+ ions were synthesized by hydrothermal method. The XRD, luminescence and excitation spectra have been studied at room temperature. The ratio of the 5D0→7F2 electric dipole transition intensity to the 5D0→7F1 magnetic dipole transition intensity (R) was used to evaluate the asymmetry of Eu3+ site. JuddOfelt parameters were calculated from emission spectra and were used to predict the radiative properties of 5D0→7FJ transitions also the lifetime of 5D0 level. The small values of Ω2 parameter and R ratio relate to high degree of symmetry of ligand around Eu3+ site in this material. Keywords: LaF3:Eu3+nanocrystals, luminescence, Judd-Ofelt analysis. 1. INTRODUCTION Rare earth (RE) doped crystals have attracted the attention of scientists due to their wide applications in many optical devices like lasers, light converters, sensors, high-density memories and optical amplifiers [1 - 5]. Compared to the oxide crystals, the fluoride crystals show more featured advantages such as long lifetime, weak nephelauxetic effect and low phonon energy [6 8], so these crystals are promising candidates for producing the laser and upconversion devices [4 - 6, 8]. Lanthanum fluoride nanocrystals (LaF3) are known with the maximal phonon mode frequency about 380 cm-1 [9], so they are an ideal material for RE dopant because they minimize multiphonon decay processes between .
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