Co-emission and energy transfer of Sm3+ and/or Eu3+ activated zinc-germanate- tellurite glass as a potential tunable orange to reddish-orange phosphor

Abstract

Sm3+/Eu3+ single doped and co-doped zinc-germanate-tellurite glasses were prepared by the glass melting method. Raman and optical spectroscopic properties of Sm3+, Eu3+ and Sm3+/Eu3+ doped TeO2-GeO2-ZnO glasses have been characterized through optical absorption and pulsed/steady fluorescence. Excitation and emission spectra measurements indicated that the energy transfer process Sm → Eu is active in the samples. The concentration of europium ions was varied to provide red emission for possible control over the chromaticity tuning in the red-orange region. Upon 344 nm excitation, the color of the global emission can be adjusted from orange of 2038 K to reddish-orange of 1683 K by increasing the Eu3+ content from 1 up to 2% mol, and co-doped with 0.5% mol Sm3+. Reddish-orange color purity very close to 100% is attained when the phosphors are excited at 406 nm. The time shortening of Sm3+ emission decay in the presence of Eu3+ was attributed to a Sm3+ → Eu3+ non-radiative energy transfer process. From fitting the Sm3+ emission decay profile with the Inokuti-Hirayama model, it was inferred that the energy transfer process could be dominated by an electric dipole-dipole interaction.