Abstract
The coordination state of Ge ions in PbO-GeO2 glasses was examined using EXAFS. It was found that a part of Ge ions changed from 4-fold to 6-fold coordination state on addition of PbO, which had been expected from the property-composition relations. The fraction of 6-fold coordinated Ge ions, N6, increased with increasing PbO content up to 20mol%, then decreased on further increase in PbO content. However, the maximum N6 was about 13% and twice as small as that in binary alkali germanate glasses. The refractive index of the glasses, n, increased with increasing PbO content, showing a very faint hump around 20mol% PbO, and third-order nonlinear optical susceptibility, χ(3), monotonously increased from 1.0×10-13 esu at PbO=0 to 5.6×10-13 esu at PbO=40mol% with an increase in PbO content. The absence of germanate anomaly in nor χ(3)-composition relation was explained by the smaller effect of change in coordination state of Ge ions in comparison with that by PbO addition.
