T. Komatsu et al., THERMAL-STABILITY AND HOPPING CONDUCTION IN BI4SR3CA3CUXOY GLASSES (X=4-9), Journal of non-crystalline solids, 195(1-2), 1996, pp. 102-112
The thermal stability and transport properties of Bi(4)Sr(3)Ca3Cu(x)O(
y) glasses with different Cu contents, 4 less than or equal to x less
than or equal to 9, and Cu valence states, R(Cu+>=Cu+/(Cu++Cu2+) With
0.7 less than or equal to R less than or equal to 1, have been examine
d. The Cu content dependence of thermal stability, electrical conducti
vity and activation energy for conduction is not monotonic, but the ma
gnitudes of these properties change at the composition x congruent to
6.5: The effect of R(Cu+) on the conduction of Bi-Sr-Ca-Cu-O glasses h
as been measured and the conductivity is analyzed using the Mott equat
ion for electron conduction of glasses containing transition metal ion
s; the results suggest that the polaron hopping mechanism between Cuand Cu2+ is appropriate for the conduction of all Bi(4)Sr(3)Ca(3)Cu(x)
Oy glasses irrespective of Cu content. A new structure model, particul
arly on the role of Cu+, has been proposed for the present glasses, in
which Cu+ ions act as both network formers and modifiers depending on
the ratio of Cu+/Bi3+.