Novel high color-purity Eu3+-activated Ba3Lu4O9 red-emitting phosphors with high quantum efficiency and good thermal stability for warm white LEDs

Abstract

In this work, a series of novel Eu3+-activated Ba3Lu4O9 red phosphors were synthesized via a traditional high-temperature solid-state reaction method and their phase purity, crystal structure, morphologies, luminescence properties, thermal stability, and internal quantum efficiency were characterized in detail. All the samples showed intense red emission band with a primary peak centered at around 614 nm when excited by near-ultraviolet light at 396 nm. What's more, the optimal Eu3+ doping concentration in the Ba3Lu4O9 host was 25 mol% with a corresponding internal quantum efficiency up to 82%. The CIE chromaticity coordinates of Ba3Lu4O9:0.25Eu3+ sample were calculated to be (0.6687, 0.3307), which were very close to that of ideal red light. Moreover, the color purity of Ba3Lu4O9:0.25Eu3+ sample was determined to be as high as 98%. Meanwhile, Ba3Lu4O9:Eu3+ phosphors also possessed good thermal stability and the emission intensity at 423 K still remained about 64% of that at initial temperature. Finally, a prototype warm white light-emitting diode (LED) lamp with a high value of color render index (~94) and low correlation color temperature (~ 3051 K) was fabricated by coating blue phosphors (BaMgAl10O17:Eu2+), green phosphors ((Ba,Sr)2SiO4:Eu2+), and red phosphors (Ba3Lu4O9:Eu3+) on a 395 nm near-ultraviolet-emitting LED chip. Consequently, the results indicated that the as-obtained red-emitting Ba3Lu4O9:Eu3+ phosphors were promising red components for warm white LEDs.