Red Emitting Ca2GeO4:Eu3+ Phosphors for Field Emission Displays

Abstract

A novel red emitting phosphor, Eu3+-doped Ca2GeO4 was prepared through the solid state reaction. We also replace Ca2+ with Mg2+ and Ba2+ ions and add Li+, Al3+ ions as charge compensators in the Ca2GeO4 host to improve the luminescence properties of Ca2GeO4:Eu3+ phosphor. XRD, FE-SEM, photoluminescence and cathodoluminescence spectra were utilized to characterize the samples. XRD reveals that pure Ca2GeO4 phase can be obtained at 1250°C and all the above cation substitutions can be achieved in a certain concentration range except for Ba2+ ion. FE-SEM images indicate that the Ca1.99GeO4:0.01Eu3+ sample and its substitutions consist of aggregated particles with size ranging from 0.5 to 2 μm, and Ba1.99GeO4:0.01Eu3+ sample is composed of uniform and spindle-like structures with the size ranging from 300 to 500 nm. Under the excitation of ultraviolet light and low-voltage electron beams, the Ca2GeO4:Eu3+ phosphor shows the characteristic emissions of Eu3+ (5D0–7F2 at 613 nm, red). The optimum concentration for the luminescence Eu3+ is determined to be 0.01 in Ca2−xGeO4:xEu3+ phosphor. The luminescent intensity can be improved by co-doping the Mg2+ ions and charge compensators (Li+ and Al3+) to partially substitute of Ca2+ ions.