The FTIR results indicated a deformation of the lead borate based glasses with the replacement
of PbO by Bi2O3 which was attributed to the appearance of Bi–O stretching vibrations in [BiO6] structural units
and generated excess of non-bridging oxygens. This deformation affected the [BO3] units which are indicated
fromthe lower decreasing rate of N4 as a function of Bi2O3.