Effect of boron oxide addition on the Nd3+ environment in a Nd-rich soda-lime aluminoborosilicate glass

Abstract The environment of Nd 3+ ions has been studied using optical absorption spectroscopy and EXAFS at the Nd L 3 -edge, in a series of soda lime aluminoborosilicate glasses with increasing B 2 O 3 content. The proportion of BO 4 units has been determined by 11 B MAS NMR in an equivalent glass series with La 3+ ions replacing the majority of Nd 3+ ions, and complementary information has been obtained by measuring the Nd 3+ decay fluorescence times in these latter glasses. In these glasses with low Al 2 O 3 content, the R′ ratio, with R′ = [Na 2 O exc ] / [B 2 O 3 ] and [Na 2 O exc ] = [Na 2 O] − [Al 2 O 3 ] − [ZrO 2 ], plays a key role in controlling the structural organization and crystallization resistance, in a similar way as the R ratio in the Dell and Bray model of sodium borosilicate glasses. At R′ > 0.5, the Nd 3+ ions are located in a mixed silicate–borate environment and, by slow cooling of the melt, they tend to crystallize within a silicate apatite phase close to the Ca 2 Nd 8 (SiO 4 ) 6 O 2 composition. At R′ 3+ ions located in a borate-type environment (not excluding Si neighbors), and, by slow cooling of the melt, they segregate with Ca 2+ ions within a Si-depleted separated borosilicate phase.