Structural study on peculiar high-pressure behavior of fluorozirconate glass in permanent densification Original Research Article

A 55ZrF4·17BaF2·23NaF·5EuF3 glass was densified under 1.5, 3.0, 4.5, 6.0, and 9.0 GPa at 250°C by using a 6–8 multi-anvil-type high-pressure apparatus. The densities of permanently densified glasses increased until exhibiting a maximum value around 3.0 GPa and then gradually decreased with further increasing pressure. Local structures around Zr4+, Eu3+, and Ba2+ in the undensified and densified glasses were investigated by means of Raman spectroscopy, Eu3+ fluorescence spectroscopy, and Zr–K, Eu–LIII, and Ba–LIII EXAFS spectroscopy. The EXAFS analyses revealed that the local structure around Ba2+ changed remarkably with applied pressure, giving a pressure dependence similar to that of density, while the local structures around Zr4+ and Eu3+ hardly changed. Therefore, it is concluded that the structural change around Ba2+, which is explained by a structural relaxation in the F− coordination environments around Ba2+ under releasing applied pressure, is an origin of a peculiar high-pressure behavior observed in the present glass.