Structure and properties of hafnium iron borophosphate glass-ceramics

Effects of hafnium addition on the structure and properties of iron borophosphate glasses with nominal composition of xHfO2-yB2O3-[40-(x + y)]Fe2O3-60P2O5 (x = 0-8, mol%) and xHfO2-yB2O3-[40-(x + y)][40Fe2O3-60P2O5] (x = 2-6, mol%) have been investigated by XRD, DTA, IR, SEM and Mössbauer spectroscopy. There were some surface crystallizations on some of the samples containing high amounts of Hf and B. XRD spectra revealed that HfP2O7 crystallized in the glass matrix when HfO2 content was above 2 mol% even when there was no surface crystallization and samples looked glassy. SEM-EDAX image-analyses supported the formation of the HfP2O7 phase. Dissolution rates of Hf-containing iron borophosphate glasses were in the 10− 9-10− 10 g/cm2 min range which shows that the existence of the crystalline HfP2O7 phase in the glass matrix has not degraded the aqueous chemical durability of these glasses. The band observed at ~ 984 cm− 1 in the IR spectra of Hf containing samples was attributed to the Hf-O-P bonds in HfP2O7. Iron existed in two valence states, i.e. Fe2 + and Fe3 + and Mössbauer hyperfine parameters indicated that both ions have octahedral coordinations in the samples studied.