Abstract

The strengths of fibers drawn from three metaphosphate glasses [NaPO ₃, Zn(PO ₃) ₂ and a Schott laser glass, LG 770, with the approximate molar composition 20K ₂O-10MgO-10Al ₂O ₃-60P ₂O ₅] and a pyrophosphate (P ₂O ₇) glass of nominal composition 40FeO ₃-60P ₂O ₅ have been measured in 2-point bending at room temperature and at 77 K. While the three metaphosphate glasses have relatively smaller strengths at low temperature (∼3 GPa), the iron phosphate glass has a strength at this temperature (∼6 GPa), 1/2 that of silica (13 ± 2 GPa). No correlation was found with either the square root of Young's modulus (E) ^1/2 or fracture toughness (K _IC), but an understanding of the results was obtained by considering the overall integrity of the individual glass networks.