Eu2+/Eu3+-doped oxyfluoride glass ceramics with LaF3 for white LED color conversion

Abstract

SiO2–Na2O–Al2O3–LaF3 glasses doped with Eu2+ and Eu3+ were synthesized to realize an inorganic color converter for white LED using 400nm UV LED. Among various rare earth ions, Eu2+ and Eu3+ showed prominent emission under 400nm LED excitation. Carbon and EuF3 content were varied to control the ratio of Eu2+ and Eu3+ during the melting process. When the ratio of Eu2+ and Eu3+ within the glass matrix was properly controlled, color coordinates of the photoluminescence spectra could be adjusted to make white colors under 400nm LED excitation. The emission intensity was increased with subsequent heat treatment which led to the formation of LaF3 nano-crystals. However, almost no conversion was observed when the glasses were actually mounted on UV-LED to make a white LED. Heavy crystallization of the oxyfluoride glasses was thus investigated to improve its scattering of the light source and color conversion efficiency, and its practical feasibility as an inorganic UV-LED color converter was demonstrated.