Effect of ionic bond in recording materials on characteristics of phase-change optical disk

This paper discusses a crystallization model that takes difference of covalent bond and ionic bond into consideration. Ionic bond makes crystallization easier than covalent bond because ionic bond is more flexible than covalent bond. The diameter and spaces around large minus-ions should also be taken into consideration. Elements having electronic negativity far from that of Te or Sb has a tendency to form ionic bonds. For example, Th and In are considered to make chemical bonds having more ionic characteristics than Ge. In the case of already reported Sn or Bi addition, large ion diameter seems to increase crystallization speed.