Tunable dual‐mode emission with excellent thermal stability in Ca ₄ ZrGe ₃ O ₁₂ :Eu phosphors prepared in air for NUV‐LEDs

Abstract

Abstract Novel dual valence Eu‐doped Ca 4 ZrGe 3 O 12 (CZGO) phosphors were successfully fabricated in air atmosphere through a solid‐state route. Their crystal structure, photoluminescence properties as well as thermal quenching performance were investigated systematically. The spectra show that part of Eu 3+ were reduced to Eu 2+ and the mechanism is interpreted by the charge compensation. By altering Eu concentration, multi‐color luminescence covering from blue to red is realized when irradiated by 370 nm light, which perfectly matches with the near ultraviolet (NUV) light‐emitting diode (LED) chips. More importantly, under NUV excitation, luminescent intensities are almost unchanged even up to 423 K. And chromaticity exhibits only a tiny shift with growing temperature. Such suitable luminescent spectra and superior thermal stability indicate that CZGO:Eu phosphors are promising candidates for blue‐red components in NUV pumped W‐LEDs. Finally, the fabricated W‐LED based on the combination of CZGO:Eu phosphors, Ba 2 SiO 4 :Eu 2+ and a 365 nm NUV‐LED chip gives a high color rendering index, a low correlated color temperature and suitable CIE chromaticity coordinates.