Novel color tunable LaCaGaO <sub>4</sub> :Bi <sup>3+</sup> ,Eu <sup>3+</sup> phosphors for high color rendering warm white LEDs
Zheng Lu, Dashuai Sun, Zeyu Lyu, Sida Shen, Pengcheng Luo, Shuai Wei, Luhui Zhou, Hongpeng You
Abstract
Abstract A series of LaCaGaO 4 : x Bi 3+ , y Eu 3+ ( 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 LaCaGaO 4 : x Bi 3+ phosphor shows an intense blue emission under near‐ultraviolet excitation, originating from the 3 P 1 → 1 S 0 transition. The spectrum analysis reveals that the Bi 3+ ions occupy two luminescence centers in the LaCaGaO 4 host and that energy transfer can occur. A model of the energy transfer between the Bi 3+ and Eu 3+ ions was also created and studied in detail. As the Eu 3+ ‐concentration increased, the emission color of the LaCaGaO 4 :0.005Bi 3+ , y Eu 3+ 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 R a 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.