50CuO(x)-50P(2)O(5) glasses with different copper valence states (0 <
Cu+/(Cu2+ + Cu+) < 0.61) were prepared by adding glucose during glass
melting, and some physical properties and fragility of these glasses w
ere examined. The density of 50CuO(x)-50P(2)O(5) glasses decreases lin
early with increasing Cu+ content from 3.18 to 3.01 g/cm(3). Although
the glass transition temperature decreases with increasing Cu+ content
from 437 to 196 degrees C, the viscosity and the activation energy fo
r viscous flow also decrease with increasing Cu+ content. From the con
cept of fragility, it was found that 50CuO(x)-50P(2)O(5) supercooled l
iquids become strong with increasing Cu+ content due to the formation
of strong Cu+-O bonds. The properties of 50CuO(x)-50P(2)O(5) glasses w
ere compared with those of xNaO(0.5)-(50-x)MgO-50P(2)O(5) glasses, and
the results suggest that the former glasses exhibit unique properties
and fragility due to a unique coordination state of Cu+.