Spectroscopic properties and ab initio calculations on the structure of erbium–zinc-borate glasses and glass ceramics

Glasses in the (Er2O3)x·(B2O3)(60 − x)·(ZnO)40 system (0 ≤ x ≤ 15 mol%) have been prepared by the melt quenching technique. X-ray diffraction, FTIR spectroscopy, UV-VIS spectroscopy and ab initio calculations studies have been employed to study the role of Er2O3 content on the structure of the investigated glass system. diffraction and infrared spectra of the glasses reveal that the B–O–B bonds may be broken with the creation of new non-bridging oxygen ions facilitating the formation of Er–O–B linkages. The excess of oxygen can be accommodated in the network by the conversion of sp2 planar [BO3] units to the more stable sp3 [BO4] tetrahedral structural units. The linkages of the [BO4] structural units can polymerize in [B3O9]− 9 cyclic trimeric ions which will produce the ErBO3 crystalline phase. An increase of the efficiency corresponding to the 4I15/2 state to 4I11/2 state (4f–4f) transitions of Er+ 3 ions was observed for the erbium oxide richest glasses. tio calculations on the structure of the matrix network show the thermodynamic instability of the [BO4], [ZnO4] and [Zn4O] structural units. Formation of three-coordination oxygens was necessary to compensate shortage of oxygens from zinc ions.