New Single-Phase, White-Light-Emitting Phosphors Based on δ-Gd₂Si₂O₇ for Solid-State Lighting

Abstract

Two new white-light (WL)-emitting phosphors (δ-Gd2Si2O7:Dy and δ-Gd2Si2O7:Eu,Tb) have been synthesized by the sol–gel method. The Gd-Ln3+ (Ln3+= Dy3+, Tb3+, Eu3+) energy-transfer band has been used to excite both phosphors, which provides an enhancement of the Ln3+ emissions. First, WL was generated from δ-Gd2Si2O7:xDy thanks to the particular ratio of the blue and yellow emissions observed in all three compositions, which had chromatic coordinates of x = 0.30, y = 0.33 and CCT values of between 7077 and 6721 K. The decay curves of the main transitions of Dy3+ showed a maximum lifetime value for δ-Gd2Si2O7:0.5%Dy, which is, therefore, the most efficient doping level. Second, a broad spectral range, single-phase, WL-emitting phosphor was generated by codoping δ-Gd2Si2O7 with Tb3+ and Eu3+. The composition δ-Gd2Si2O7:0.3%Eu3+;0.8%Tb3+ showed CIE coordinates well inside the ideal WL region of the CIE diagram and a CCT value of 5828 K. The single-phase WL-emitting phosphors presented in this paper are promising materials to be used in white solid-state lighting systems and field-emission displays due to the advantages provided both by Gd3+ ions and by the high thermal and chemical stabilities of the rare earth disilicate matrix.