Photoluminescence from the 5D 4 level of Tb 3+ ions in K–Ba–Al fluorophosphate glass under pressure

Abstract

Fluorescence spectra of Tb 3+ ions in 55.5P 2O 5–17K 2O–14.5BaO–8Al 2O 3–4AlF 3–1.0Tb 4O 7 (PKBAFTb) glass have been measured as a function of high pressures up to 35 GPa at room temperature. A strong red shift of 5D 4 → 7F J ( J = 3, 4 and 5) transitions with different rates is observed under pressure, which is attributed to the increasing spin–orbit coupling constant, ζ 4f. There is a considerable pressure effect on the magnitude of the crystal-field splittings observed for the 5D 4 → 7F 4 and 7F 5 transitions. The increase in Stark splittings observed under pressure is due to pressure induced electrostatic interaction between the 4f electrons and their ligands. Decay times of the emission from the 5D 4 level fit to a single exponential function for the entire pressure range studied. Analyses indicate that the luminescence properties under pressure are more or less reversible, which shows the absence of considerable hysteresis in the present studied glass.