Enhancement of luminescence properties in Er 3+ doped TeO 2–Na 2O–PbX (X = O and F) ternary glasses

Abstract

An enhancement of luminescence properties in Er 3+ doped ternary glasses is observed on the addition of PbO/PbF 2. The infrared to visible upconversion emission bands are observed at 410, 525, 550 and 658 nm, due to the 2H 9/2 → 4I 15/2, 2H 11/2 → 4I 15/2, 4S 3/2 → 4I 15/2, 4F 9/2 → 4I 15/2 transitions respectively, on excitation with 797 nm laser line. A detailed study reveals that the 2H 9/2 → 4I 15/2 transition arises due to three step upconversion process while other transitions arise due to two step absorption. On excitation with 532 nm radiation, ultraviolet and violet upconversion bands centered at 380, 404, 410 and 475 nm wavelengths are observed along with one photon luminescence bands at 525, 550, 658 and 843 nm wavelengths. These bands are found due to the 4G 11/2 → 4I 15/2, 2P 3/2 → 4I 13/2, 2H 9/2 → 4I 15/2, 2P 3/2 → 4I 11/2, 2H 11/2 → 4I 15/2, 4S 3/2 → 4I 15/2, 4F 9/2 → 4I 15/2 and 4S 3/2 → 4I 13/2 transitions, respectively. Though incorporation of PbO and PbF 2 both enhances fluorescence intensities however, PbF 2 content has an important influence on upconversion luminescence emission. The incorporation of PbF 2 enhances the red emission (658 nm) intensity by 1.5 times and the violet emission (410 nm) intensity by 2.0 times. A concentration dependence study of fluorescence reveals the rapid increase in the red ( 4F 9/2 → 4I 15/2) emission intensity relative to the green ( 4S 3/2 → 4I 15/2) emission with increase in the Er 3+ ion concentration. This behaviour has been explained in terms of an energy transfer by relaxation between excited ions.