Alkali fluoride dependence of fluorine coordination environment of zirconium in fluorozirconate glasses

Abstract

The F coordination environments of Zr in crystalline alkali fluorozirconates differ greatly with alkali ion species. If similar circumstances could be developed in fluorozirconate glasses by choosing and/or combining alkali fluoride species, it would lead to the ability to design specific structures in fluorozirconate glass. In order to test this possibility in fluorozirconate glasses, the variation of the F coordination environments of Zr with changing alkali fluorides was examined on compositions 42.5MF·52.5ZrF 4·5.0LaF 3 (M: Li, Na, K, Rb and Cs) and xLiF·(95.0−x)ZrF 4·5.0LaF 3 (x: 20.0∼47.5) in mol% by Zr-EXAFS using Synchrotron Orbital Radiation (SOR). The F coordination number of Zr was almost the same for all alkali fluoride species. On the other hand, the average ZrF interatomic distance shortened as the alkali ion radius became larger. In the K, Rb and Cs glasses, moreover, the ZrF interatomic distances were divided into two groups. Although these alkali fluoride variations were entirely different from those observed in crystalline alkali fluorozirconates, designing the F coordination about Zr in fluorozirconate glasses was found to be possible by choosing the alkali fluoride species to be used.