OPTICAL-SPECTRA OF YB3-ND3+ INTERACTION IN CS2NAND0,4YB0,6CL6( AND YB3+)

Interaction between octahedrally coordinated Nd3+ and Yd(3+) in Cs2NaN d0,4Yb0,6Cl6 reduces the Nd3+ luminescence lifetime by roughly two ord ers of magnitude with respect to that found in Cs2NaNdCl6-. Analysis o f low temperature absorption and emission spectra reveals that the non radiative Nd3+-Yb3+ energy transfer has to be assisted by lattice phon on emission, nevertheless the rate of the transfer is high in the 4-30 0 K temperature region and attains 5.8 x 10(5)s(-1) at room temperatur e. A phase transition of Cs2NaNd0,4Yb0,6Cl6 between 12 and 13 K is evi denced by abrupt change of both the spectra and lifetimes of Yb3+. Red uction of Yb3+ lifetime from 5.3 ms to 150 mu s is at the transition f rom low symmetry phase to high symmetry phase is supposed to be associ ated with a three ion interaction which occurs in ordered lattice and disappears in low temperature disordered structure. (C) 1998 Elsevier Science B.V. All rights reserved.