Mössbauer study of europium in fluorozirconate glass

151Eu Mössbauer spectra of fluorozirconate glasses of nominal composition 0.61 ZrF4 · (0.32 - x) BaF2 · x EuF2 · 0.07 ThF4 with x = 0.10 and 0.20 show that Eu2+ is present in sites with isomer shifts in the range -15.5 to -12.9 mm/s, corresponding to EuF bond lengths of 2.3-2.8 Å and a coordination number ranging from 8 to 12. The glasses contain a minor amount (∼10%) of Eu3+ in well-defined sites. Effective Debye temperatures deduced from the recoilless fractions for the two ions are θD2+ = 145 K and θD3+ = 261 K. The differences in coordination and bonding indicate that trivalent eurpoium is a network former, whereas the divalent ions are network modifiers. © 1981.