Up-conversion luminescence of trivalent-rare-earth ion-doped LnTaO 4 (Ln = Y, Gd, La)

Abstract

The up-conversion luminescence properties of trivalent-rare-earth ion-doped orthotantalates are studied under 980 nm laser diode excitation. The results indicate that YTaO 4:Tm 3+/Yb 3+ emits blue and strong infrared emissions respectively corresponding to 1G 4→ 3H 6 and 3H 4→ 3H 6 transitions of Tm 3+ ions, while YTaO 4:Er 3+/Yb 3+ produces strong green and weak red emissions, resulting from 2H 11/2/ 4S 3/2→ 4I 15/2 and 4F 9/2→ 4I 15/2 transitions of Er 3+ ions, respectively. In contrast to three excellent up-conversion phosphors, viz. NaYF 4:Er 3+/Yb 3+, Y 2O 2S:Er 3+/Yb 3+ and Y 2O 3:Er 3+, YTaO 4:Er 3+/Yb 3+ shows not only strong green emission, but also larger intensity ratio of green to red emission. In addition, it is found that LaTaO 4: Er 3+/Yb 3+ shows the minimum quenching concentration of Yb 3+ and weakest up-conversion emission intensity, and the main peak presents blue shift (8 nm/556 nm) as compared with YTaO 4:Er 3+/Yb 3+ and GdTaO 4:Er 3+/Yb 3+. The distinct luminescent characteristics of LaTaO 4: Er 3+/Yb 3+ can be attributed to the larger difference of radius between doped ion and La 3+ ion.