Luminescent center in Br--rich BaFBr : O2-

In this work, emission, excitation and absorption spectra of pure and 1 mol % O2- -doped BaFxBr2 -x (x = 0.98, 1.0, 1.02) powders were measured. It was found that the spectra of O2- -doped Br--rich sample (x = 0.98) is differe nt from those of the other O2--doped samples (x = 1.0 and 1.02). Its emissi on peak shifts from 500 to 550 nm, and becomes much wider. Absorption spect ra show that F(Br-) centers of the X-rayed Br--rich sample, unlike those of other X-rayed samples, are not disturbed by doped oxygen. With the EPR, it is shown that O2- ions are on the F- sites in either F--rich(x = 1.02) or Br--rich sample. We suggested that in the Br--rich sample (x = 0.98) the lu minescence is due to an O-F '-V-F(.) pair, instead of the O-F'-V-Br(.) pair in other samples (x = 1.0 and 1.02). (C) 1999 Elsevier Science B.V. All ri ghts reserved.