High thermal stability of warm white emitting single phase GdPO4: Dy3+/ Sm3+ phosphor for UV excited wLEDs

Abstract

Highly thermally stable warm white light emission has been obtained from a single component phosphor; GdPO4: Dy3+/Sm3+. A series of GdPO4: Sm3+ (1%)/Dy3+ (x%) (x = 0.1, 0.5, 1 and 2) phosphors have been synthesized by the co-precipitation method. The crystal structure and phase purity of the samples obtained were verified by X-ray diffraction. Photoluminescence spectra, luminescence lifetimes are used to study the effect of Dy3+ concentration and the energy transfer from Dy3+ to Sm3+ as a function of excitation wavelength. The nearest-neighbor contributed to the non-radiative energy transfer from Dy3+ to Sm3+ in GdPO4, under 273 and 363 nm excitation. A warm white light was obtained from all phosphors excited at 273 nm and for 1 and 2% of Dy3+ in GdPO4:Sm3+ under 363 nm excitation. Temperature-dependent luminescence properties are determined for GdPO4: Sm3+ (1%), Dy3+ (1%) under 273 nm and 363 nm excitation. The studied phosphor has a good luminescence thermal stability and the determined activation energy for thermal quenching is 1.26 and 0.75 eV for 273 nm and 363 nm excitation wavelengths, respectively. The effect of the Dy3+ concentration as an activator ion responsible for the white emission light, at a fixed concentration of Sm3+ as a red emission compensator in the Dy3+ emission spectrum, was discussed. The low color temperature and high thermal stability indicate that the studied material is a promising solid-state emitting phosphors for the UV chip excited warm wLED applications.