Optical basicity analysis of glasses containing trivalent scandium, yttrium, gallium and indium

Refractivity data (densities and refractive indices) of the following ternary glasses were used to obtain the molar electronic polarisabity, α m , of each glass: Sc 2 O 3 -Na 2 O-SiO 2 , Y 2 O 3 -Na 2 O-SiO 2 , In 2 O 3 -Na 2 O-SiO 2 , Ga 2 O 3 - M 2 O-SiO 2 (where M is Li or Na) and Ga 2 O 3 -MO-SiO 2 (where M is Ca, Sr or Ba). Subtracting from α m the total cation polarisabilities, and dividing by the number of oxygen atoms assumed for the formula of the glass, provided values of the oxide (-II) polarisabilty, α o x i d e ( - I I ) - In turn, a o x i d e ( - I I ) , being related quantitatively to the optical basicity, A, of the glass, allowed calculation of the basicity moderating parameter, γ M , for each of the tripositive metal ions: scandium (1.1), yttrium (1-0), gallium (1-4) (these figures to the nearest 0-05). Results obtained for In 3 + were inconsistent, but an interpolated value of 1-05 was obtained when y values for Al 3 + , Sc 3 + , Y 3 + , Ga 3 + , La 3 + and Lu 3 + were plotted against cation charge/cation radius. The y values for Sc 3 + , Y 3 + and In 3 + are similar to those of Ca 2 + (1.00) or Mg 2 + (1.15); yfor Ga 3 + signifies greater polarising power, close to that of Al 3 + (γ A 1 =1.5).