Zinc phosphate glasses activated with Dy3+/Eu3+/Sm3+ and Tb3+/Eu3+/Sm3+ for reddish-orange and yellowish white phosphor applications

Abstract

Spectroscopic evaluations of Dy3+/Eu3+/Sm3+ and Tb3+/Eu3+/Sm3+ doped zinc phosphate glasses, based on excitation and emission spectra, and emission decay measurements, are particularly focused on potential white light-emitting diodes applications. All the excitation wavelengths located in the 337–382 nm range, match with the emissions of AlGaN, GaN and InGaN LEDs. The Dy3+/Eu3+/Sm3+ doped zinc phosphate glass excited at 347 nm displays yellowish white tonality according with the x = 0.396 and y = 0.408 CIE1931 chromaticity coordinates and correlated color temperature (CCT) value of 3837 K, whereas under 362, 374 and 382 nm excitations, it displays reddish-orange tonality with CIE1931 chromaticity coordinates (and CCT values): x = 0.503 and y = 0.398 (2075 K), x = 0.570 and y = 0.388 (1640 K), and x = 0.527 and y = 0.386 (1804 K), respectively, with color purities higher than 72%. The Dy3+ and Sm3+ emission decay analysis suggests that non-radiative energy transfer processes from Dy3+ to Eu3+ and/or Sm3+ and Sm3+ to Eu3+ take place with efficiencies of 0.09 ± 0.04 and 0.15 ± 0.04, respectively. The Dy3+ and Sm3+ emission decay fitting by the Inokuti-Hirayama model, indicates that electric dipole-quadrupole and quadrupole-quadrupole interactions might respectively mediate the energy transfer processes inside the Dy3+-Sm3+-Eu3+ clusters. The Tb3+/Eu3+/Sm3+ doped zinc phosphate glasses only exhibits reddish-orange emission tonality with CIE1931 chromaticity coordinates and (CCT values): x = 0.510 and y = 0.425 (2210 K), x = 0.549 and y = 0.399 (1754 K), x = 0.510 and y = 0.411 (2108 K), and x = 0.544 and y = 0.385 (1710 K), under 337, 361, 374 and 380 nm excitations, respectively, with color purities higher than 79% in all cases. The Tb3+ and Sm3+ emission decay shortening in presence of Sm3+ and Eu3+, and Tb3+ and Eu3+, respectively, points out Tb3+→ Eu3+ and/or Sm3+ and Sm3+ → Eu3+ non-radiative energy transfers, with efficiencies of 0.08 ± 0.04 and 0.04 ± 0.05, respectively. The Inokuti-Hirayama model suggests that the Tb3+→ Eu3+ and/or Sm3+ and Sm3+ → Eu3+ energy transfer processes might be, respectively, dominated by electric dipole-quadrupole and quadrupole-quadrupole interactions inside Tb3+-Sm3+-Eu3+ clusters.