ZrO 2 addition in soda-lime aluminoborosilicate glasses containing rare earths: Impact on the network structure

The influence of increasing ZrO 2 content on the structural features of a rare earths (RE ¼ Nd, La) bearing soda-lime aluminoborosilicate glass was investigated through a multi-spectroscopic approach (Raman, Zr-EXAFS, 29 Si, 11 B, 27 Al and 23 Na MAS NMR). Particular attention was paid to the modifications occurring in the glassy network and on the distribution of Na þ and Ca 2þ ions. Zr 4þ ions were shown to be located in (ZrO 6) 2A sites, connected to the silicate network, and preferentially charge compensated by Na þ ions. A favorable competition of Zr 4þ ions against RE 3þ ions and (BO 4) A entities for charge compensators was observed, but no effect was detected on the environment of (AlO 4) A entities. This competition resulted in a modification of the RE 3þ ions environment with the ZrO 2 content that may affect their solubility in the glassy network.