Peculiar high-pressure behavior in permanent densification of fluorozirconate glass

A 60ZrF4·30BaF2·10EuF3 glass was densified under 1.5, 3.0, 4.5, 6.0, and 9.0 GPa at 250°C using a 6–8-type multi-anvil high-pressure apparatus. The densities of permanently densified glasses exhibit a maximum value at the 3.0 GPa treatment and then a marked decrease with increasing pressure. Such a peculiar permanent densification behavior, being reported for the first time to the best of our knowledge, is discussed based on the F− coordination environments around Zr4+, Eu3+, and Ba2+. This behavior may be attributed to a spontaneous structure-relaxation.