Novel highly efficient and thermally stable Ca2GdTaO6:Eu3+ red-emitting phosphors with high color purity for UV/blue-excited WLEDs

Abstract

Nowadays, it is very stringent to develop high-performance red-emitting phosphors to accelerate the new generation of high-power white light-emitting diodes (WLEDs). In this regard, we synthesized novel highly efficient Eu3+-activated double perovskite Ca2GdTaO6 phosphors via a conventional solid-state reaction method. The phosphors possessed pure phase according to the analysis of their X-ray diffraction patterns. Under 396 nm near-ultraviolet light or 466 nm blue light excitation, they exhibited a dominant red emission centering at 615 nm, and the values for intensity ratio of red to orange emission of Ca2Gd1-xTaO6:xEu3+ samples were very high, which indicated that Eu3+ ions occupied low symmetric sites in this host. Besides, the CIE chromaticity coordinates of the optimal sample Ca2Gd0.6TaO6:0.4Eu3+ were calculated to be (0.6676, 0.3321) and the color purity could reach up to a high value of 96%. And the internal quantum efficiencies were determined to be 82% and 83% when excited at 396 and 466 nm, respectively. What's more, the thermal quenching effect on the emission spectra of Ca2Gd0.6TaO6:0.4Eu3+ phosphors excited at 396 and 466 nm were also characterized and the corresponding emission intensities at 423 K remained 78% and 82% of that at room temperature, respectively. Consequently, the results indicated that the as-obtained red-emitting Ca2GdTaO6:Eu3+ phosphors were promising red components for warm WLEDs.