A novel high-brightness red phosphor Ca4Nb2O9: Eu3+ for WLEDs

Abstract

In this study, new phosphors Ca4Nb2O9 doped with Europium (Eu3+) ions were created using a high-temperature solid-state method. Characterizations with X-ray diffraction (XRD), Rietveld refinement, scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS) and elemental mapping revealed successful doping and uniform elemental distribution. The band gap is 4.17 eV for Ca4Nb2O9 and 3.73 eV for Ca3.7Nb2O9: 0.3Eu3+, which is shown that the band gap decreases with increasing concentration. Subsequently, the samples underwent photoluminescence (PL) spectra testing, revealing that the Ca4Nb2O9: Eu3+ phosphors exhibited intense red emission when excited at 395 and 465 nm. Meanwhile, the principal emission peak resided at 613 nm, and the ideal doping concentration of Eu3+ was determined to be x = 0.3. In addition, at 420 K, the luminous intensity of Ca3.7Nb2O9: 0.3Eu3+ under 395 and 465 nm excitation is 60 % as well as 82 % of its strength at 300 K, respectively, indicating excellent thermal stability. Furthermore, the phosphor exhibits a relatively high quantum efficiency, reaching 45.47 % when excited with 395 nm light and 58.17 % when excited with 465 nm light. Finally, a white light-emitting diode (WLED) device with a Ra value of 86.3 and correlated color temperature (CCT) of 4450 K was fabricated. The results suggest that the prepared phosphor, in combination with a near-ultraviolet (NUV) light-emitting diode (LED) chip, has the potential for application in white light-emitting diodes.