Contrasting behaviour of the co-activators in the luminescence spectra of Y2O2S:Tb3+,Er3+ nanometre sized particles under UV and red light excitation

Abstract

Nanometre sized particles of terbium and erbium co-doped yttrium oxysulfide up-converting phosphors were prepared by a urea homogeneous-precipitation method. Results from X-ray powder diffraction (XRPD), scanning electron microscopy (SEM) and photoluminescence spectroscopy studies on the microstructure and luminescent properties of the materials are reported. Upconversion emission was observed from the Er³⁺ cations when particles were excited with laser light of 632.8 nm wavelength. Under these conditions no interactions between the Er³⁺ cations and the Tb³⁺ cations were observed. In contrast there was evidence from the Stokes emission of the Er³⁺ cations under 254 nm excitation for an interaction between the Er³⁺ and Tb³⁺ cations reducing intensity of the latter's blue and green emission bands by cross relaxation processes.