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

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+ con-centration 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 lumi-nescence 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.