Luminescent Properties Studies on Multicolor Emission of Single-Phase Ca9ln(Po4)7: Eu2+/3+(Ln = Y, La) Phosphors

Abstract

A series of single-phased emission-tunable Ca9Ln(PO4)7:Eu2+/3+(Ln = Y, La) phosphors were synthesized by a high temperature solid-state reaction in a CO atmosphere, and its luminescent properties have been investigated. The phosphors can be well excited in the wavelength range of 245-475 nm, which match well with the  n-UV chip. Additionally, Eu2+ and Eu3+ ions exist in Ca9Ln(PO4)7 : Eu2+/3+(Ln = Y, La), although the samples are prepared at the reducing atmosphere. The tunable emission colors of the phosphors can be achieved by varying the Eu ion concentration or excitation wavelength. The corresponding color hue of Ca9Y(PO4)7 : xEu (x = 0.01~0.2) phosphors shifts gradually from green to white and eventually to orange-red with the Eu concentration increases, whether at 252nm, 300nm or 395nm excitation. While the colour coordinates of Ca9La(PO4)7 : 0.08Eu phosphor by changing the excitation wavelength, varied the emission hue of the phosphor from orange-red to yellow-green to white, and eventually back to orange-red again. These results demonstrated that the single-component of Ca9Ln(PO4)7:Eu2+/3+(Ln = Y, La) phosphor may be candidates for w-LED multi-color phosphors.

Keywords: luminescent properties, coexistence of Eu2+ and Eu3+ ions, color-tunable phosphors