Na2Dy4(1-x)Eu4x(WO4)7 형광체의 합성과 분광학 특성

Abstract

Na2Dy4(1-x)Eu4x(WO4)7 phosphors were synthesized via a solid state reaction method. The X-ray diffraction (XRD) was used to analyze the structural characteristics of the Na2Dy4(1-x)Eu4x(WO4)7 lattices. The excitation and emission spectra and decay curves of Na2Dy4(1-x)Eu4x(WO4)7 (x = 0.01 ~ 1) were measured at room temperature. The charge transfer band (CTB) in the wavelength region 200 – 310 nm is observed in the excitation spectra. The excitation lines observed at 318, 361, 381, 393, 415 and 464 nm are attributed to the 7F0→ 5H7, 7F0 → 5D4, 7F0 → 5L7, 7F0 → 5L6, 7F0 → 5D3 and 7F0 → 5D2 transitions of Eu3+, respectively. The excitation lines at 326, 352, 366, 427, 453 and 473 nm are attributed to the 6H15/2 → 6P3/2, 6H15/2 → 6P7/2, 6H15/2 → 6P5/2, 6H15/2 → 4G11/2, 6H15/2 → 4I15/2 and 6H15/2 → 4F9/2 transitions of Dy3+, respectively. The emission spectra were measured under excitation at 266 nm (Dy3+- O2- CT band) and at 280 nm (Eu3+- O2- CT band) and at 393 nm (7F0 → 5L6). The emission lines at 591, 615, 654, and 702 nm are attributed to the 5D0 → 7F1, 5D0 → 7F2, 5D0 → 7F3 and 5D0 → 7F4 transition of Eu3+. The strongest peak at 615 nm is due to the electric dipole 5D0→ 7F2 transition of Eu3+. The emission lines at 486, 575 and 665 nm are attributed to the 4F9/2 → 6H15/2, 4F9/2 → 6H13/2 and 4F9/2 → 6H11/2 transition of Dy3+. The strongest peak at 575 nm is due to the electric dipole 4F9/2 → 6H13/2 transition of Dy3+. The decay time of the Eu3+ emission is estimated to be about 1 ms and that of the Dy3+ emission is estimated to be about 0.5 ms in the Na2Dy4(1-x)Eu4x(WO4)7 phosphor. No energy transfer occurs between Eu3+ and Dy3+ ions under excitation at the CT bands of Eu3+ or Dy3+. The luminescence intensity increases with Eu3+ concentration up to 70 mol%. No energy transfer occurs between Dy3+ and Eu3+ ions in the full Eu3+ concentration range of 0.1 – 50 mol%.