Tunable luminescence of Ce3+/Mn2+-coactivated Ca2Gd8(SiO4)6O2 through energy transfer and modulation of excitation: potential single-phase white/yellow-emitting phosphors

Abstract

Ce³⁺/Mn²⁺-coactivated Ca₂Gd₈(SiO₄)₆O₂ (CGS) oxyapatite phosphors have been prepared via high temperature solid state reaction process. The Ce³⁺ emission at different lattice sites has been identified and discussed. The energy transfer from Ce³⁺ to Mn²⁺ in CGS : Ce³⁺/Mn²⁺ phosphors has been validated and demonstrated to be a resonant type via a dipole-quadrupole mechanism, and the critical distance (R_C) calculated by quenching concentration method and spectral overlap method are 9.4 Å and 9.2 Å, respectively. A color-tunable emission in CGS : Ce³⁺/Mn²⁺ phosphors can be realized by the modulation of excitation wavelengths, namely, the change of Ce³⁺ emission at different lattice sites and the relative PL intensity of Ce³⁺ and Mn²⁺. In addition, the cathodoluminescence (CL) properties of CGS : Ce³⁺/Mn²⁺ phosphors including the CL spectra, the dependence of CL intensity on accelerating voltage and filament current, the decay behavior of CL intensity under electron bombardment, and the stability of CIE chromaticity coordinate have been investigated in detail. The results indicate that the as-prepared CGS : Ce³⁺/Mn²⁺ phosphors have a good CL intensity stability and CIE coordinate stability with a color-tunable emission from blue to yellow, crossing the white area by the energy transfer from Ce³⁺ to Mn²⁺ under low-voltage electron beam excitation. In conclusion, the wide-ranged white light with varied hues have been obtained in Ce³⁺ and Mn²⁺ coactivated CGS phosphors by utilizing the principle of energy transfer and properly designed activator contents as well as the selection of excitation wavelength under UV (287–352 nm) and low-voltage (1–7 kV) electron beam excitation. Therefore, the CGS : Ce³⁺/Mn²⁺ phosphors may potentially be used as single-phased white/yellow-emitting phosphor for UV LEDs (light emitting diodes) and FEDs (field emission displays).