희토류 이온이 도핑된 삼성분 붕산염 형광체의 합성 및 분광학 특성

Abstract

The phosphors of KBaY(BO3)2 and NaBaY(BO3)2 doped with Eu3+ and Dy3+ ions were prepared by solid state reaction method. The phase formations were confirmed by the X-ray diffraction. Excitation and emission spectra together with time-resolved spectra were obtained by Xe-lamp and pulsed UV laser excitation at room temperature. Eu3+- and Dy3+-doped KBaY(BO3)2 lattices form solid solution up to the concentration of 100 mol%, while Eu3+- and Dy3+-doped NaBaY(BO3)2 forms single phase only up to 50 mol% Eu3+ concentration. The charge transfer (CT) band of Eu3+ peaking at 270 nm shifts to longer wavelength by increasing Eu3+ concentration. The change in peak wavelength of the CT band is about 15 nm from 0.05 to 100 mol% of Eu3+ concentration in NaBaY(BO3)2 and KBaY(BO3)2. The red shift of CT band with increasing Eu3+ concentration indicates that the energy difference between the bottom of valence band and the ground state of Eu2+ in NaBaY(BO3)2 and KBaY(BO3)2 and becomes smaller at high Eu3+ concentratin. The excitation intensity of the 4f-4f transition in the wavelength region 400-550 nm obtained by monitoring the 618 nm emission increases gradually from 0.05 to 100 mol%, while different behavior is observed for the CT band which has maximum intensity at 20 mol%. This is because the cross relaxation occurs efficiently at high Eu3+ concentration. The decay curves are single exponential for Eu3+ concentration up to 20 mol% and then the decays become nonexonential the the Eu3+ concentration higher than 20 mol% indicating that energy diffusion occurs efficiently among Eu3+ ions. The Dy3+-doped NaBaY(BO3)2 and KBaY(BO3)2 exhibit strong emission line at 581 nm due to the 4F9/2 → 6H13/2 transition. Differently from Eu3+-doped NaBaY(BO3)2 and KBaY(BO3)2, the Dy3+-doped samples exhibit the maximum intensity of the Dy3+-emission at the Dy3+-concentration of 5 mol%. The result is responsible for the cross relaxation effect which is not occurs for Dy3+-doped samples.