고상법에 의한 Ca3Gd2(BO3)4:Tb3+ 형광체의 합성과 형광 특성

Abstract

The Tb3+-ion - doped Ca3Gd2(BO3)4 phosphors were synthesized by using the solid state reaction method. The Tb3+- concentration was 0.1, 1.0, 10, and 15 mol % in Ca3Gd2(BO3)4. The formation of the Ca3Gd2(BO3)4 crystals for different Tb3+-concentrations was confirmed by x-ray powder diffraction (XRD) patterns and it was observed no obvious impurity phases. Emission and excitation spectra of Tb3+ in Ca3Gd2(BO3)4 were measured at room temperature and tt is found that the spectra depend strongly on Tb3+-concentration in Ca3Gd2(BO3)4. The absorption lines due to the 4f - 4f transitions of Tb3+ in Ca3Gd2(BO3)4 are observed in the wavelength region 200 - 400 nm in which the broad band due to 4f - 5d transition of Tb3+ is located between 10 and 300 nm. The assignments of each energy levels of the 4f8 configuration of Tb3+ in Ca3Gd2(BO3)4 are performed. The strong green emission due to the 5D4 → 7FJ (J=5 and 6) transitions and weak red emission due to the the 5D4 → 7FJ (J = 3 and 4) transitions are observed. For high Tb3+- concentration (10 and 15 mol %) cross relaxation occurs in weak. In the excitation spectra the transition lines of Gd3+ are observed indicating that energy transfer occurs from Gd3+ to Tb3+ ions under ultraviolet excitation.