“…The fraction N 4 of four coordinated boron of a glass containing 45 mol% MgO is reported as 0.2. This value is mostly the same as that of the corresponding ZnO-B 2 O 3 glass [9], but is considerably lower than for alkali-or barium borate glasses. Like the case for ZnO-B 2 O 3 glasses, where some of ZnO would form its own ZnO 4 tetrahedral units [9,10], MgO might be able to be network former in certain cases.…”