Photoluminescence properties and thermal stability of Eu3+-activated La7Ta3W4O30 red-emitting phosphors for near-UV-excited w-LEDs

Abstract

Novel trivalent europium (Eu3+)-activated La7Ta3W4O30:xEu3+ (x = 0.5 mol%–40 mol%) red-emitting phosphors were synthesized by means of a high-temperature solid-state reaction. The structure, morphology, photoluminescence, thermal-stability properties, lifetime, and color-rendering of the prepared phosphors were investigated in detail. The La7Ta3W4O30:Eu3+ phosphors show five emission peaks under near-ultraviolet (n-UV) at 397 nm, and these peaks are ascribed to the transitions of 5D0–7Fj (j = 0, 1, 2, 3 and 4) by Eu3+ ions. The optimal doping concentration of Eu3+ is 20 mol%, and the critical distance of the energy transfer between the Eu3+ ions was calculated to be 1.768 nm. The quenching temperature (T0.5) of La7Ta3W4O30:20 mol%Eu3+ is about 440 K. The quantum yield (QY) was measured to be 85.85%. The fabricated white-light-emitting diodes (w-LEDs) possess high color-rendering index (Ra) of 90, and high correlated color temperature (CCT) of 5810 K, respectively. The Commission Internationale de L' Eclairage (CIE) coordinates are (0.311, 0.322). Therefore, the prepared phosphor has a promising application for w-LEDs.