the cerianite lattice. As Si has higher
electronegativity than Mn and Ce, the difference in electronegativity
between the cations and oxygen decreases and more
shift in absorption edge is expected for silicon co-doped
samples than that of manganese containing compounds. The
change in color of CP with increasing content of doped element
accounts for the shift in absorption edge, which is caused by the
change in chemical bonding nature by incorporating higher
electronegative metal ion into the praseodymium–cerium
matrix.