Spectroscopic properties of new Yb3+-doped K5Bi(MoO4)4 crystals

This research work analyzes the spectroscopic properties of Yb3+ ion in a new oxide single crystal belonging to the potassium bismuth molybdate family with the following concentrations: K5Bi1-xYbx(MoO4)(4) (x=0.005, 0.05, 0.15). We are dealing with temperature and concentration dependences of both sigma and pi polarizations of the IR absorption and emission spectra. Raman spectra is used to interpret electronic Stark levels and vibronic levels. Concentration dependence of fluorescence lifetimes allows the measurement of the high radiative lifetime in the range 1.89-1.93 ms and shows a strong self-trapping process which has been seen up to 15% Yb3+. Competition with a non-radiative energy transfer by up-conversion process is also observed due to the presence of Er3+ ion as unexpected impurity. Yb3+ pairing and clustering has not been observed in the molybdate host in which the two distances between Bi3+ next nearest crystallographic sites seem rather too large to give any observable anti-Stokes signal by cooperative luminescence. (C) 2003 Elsevier Science B.V. All rights reserved.