Synthesis, luminescence properties and thermal stability of Eu3+-activated Na2Y2B2O7 red phosphors excited by near-UV light for pc-WLEDs

Abstract In the present work, trivalent europium (Eu 3+ ) ion activated Na 2 Y 2 B 2 O 7 red phosphors have been synthesized through high-temperature solid-state reaction. X-ray diffraction confirmed the successful formation of Na 2 Y 2 B 2 O 7 :Eu 3+ phosphors with monoclinic phase. Under near-UV light (395 nm) excitation, Na 2 Y 2 B 2 O 7 :Eu 3+ phosphors exhibited red emission around 619 nm due to the 5 D 0 → 7 F 2 transition. The intensity of the 5 D 0 → 7 F 2 transition increased with respect to Eu 3+ ions concentration in Na 2 Y 2(1-x) B 2 O 7 :xEu 3+ (0.05 ≤ x ≤ 0.5) phosphors and the luminescence quenching was observed at x  = 0.35. The critical distance (R c ) and θ were calculated to be 9.20 A and 5.07, respectively, and thus the dipole-dipole interaction could play a significant role in concentration quenching. The lifetimes of the Na 2 Y 2(1-x) B 2 O 7 :xEu 3+ phosphors were calculated for various concentrations ( x ) of Eu 3+ ions. In addition, the determined color purity of Na 2 Y 2 B 2 O 7 :0.35Eu 3+ phosphor was 98.2% and internal quantum efficiency was 36.6%. Temperature-dependent photoluminescence study showed that emission intensity at 423 K was 40.2% of its initial at room temperature. The calculated activation energy of the Na 2 Y 2 B 2 O 7 :0.35Eu 3+ phosphor was 0.16 eV. The above results strongly recommended that the Eu 3+ ions activated Na 2 Y 2 B 2 O 7 phosphors can be utilized for solid-state lighting technology such as phosphor converted white-light emitting diodes.