Novel color tunable LaCaGaO4:Bi3+,Eu3+ phosphors for high color rendering warm white LEDs

Abstract

AbstractA series of LaCaGaO4:xBi3+,yEu3+ (x = 0.002–0.04, y = 0.02–0.45) phosphors with adjustable emission colors were synthesized by high‐temperature solid‐state reaction. The samples were identified as pure phases by X‐ray diffraction and Rietveld refinement, and the crystal structures were analyzed in detail. The LaCaGaO4:xBi3+ phosphor shows an intense blue emission under near‐ultraviolet excitation, originating from the 3P1 → 1S0 transition. The spectrum analysis reveals that the Bi3+ ions occupy two luminescence centers in the LaCaGaO4 host and that energy transfer can occur. A model of the energy transfer between the Bi3+ and Eu3+ ions was also created and studied in detail. As the Eu3+‐concentration increased, the emission color of the LaCaGaO4:0.005Bi3+,yEu3+ phosphor changed from blue to pink to red. In addition, the fluorescence lifetime, quantum yield, thermal stability, and other properties of the phosphors were characterized and analyzed. Finally, two white light‐emitting diode devices with Ra values of 96.6 and 95 and correlated color temperatures of 4578 and 3324 K were fabricated, indicating the potential of phosphors for warm white lighting applications.