Structural properties of fluorozirconate-based glass ceramics doped with multivalent europium

摘要

The structure/property relationships of fluorochlorozirconate glass ceramics as a function of divalent and trivalent europium (Eu) co-doping and thermal processing have been investigated; the influence of doping ratio on the formation of barium chloride (BaCl2) nanocrystals therein was elucidated. X-ray absorption near-edge structure spectroscopy shows that the post-thermal annealing changes the Eu valence of the as-poured glass slightly, but during the melting process Eu³⁺ is more strongly reduced to Eu²⁺, in particular, when doped as a chloride instead of fluoride compound. The Eu²⁺-to-Eu³⁺ doping ratio also plays a significant role in chemical equilibrium in the melt. X-ray diffraction measurements indicate that a higher Eu²⁺ fraction leads to a BaCl2 phase transition from hexagonal to orthorhombic structure at a lower temperature.