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

Abstract

Glasses in the (Er2O3)x·(B2O3)(60−x)·(ZnO)40 system (0≤x≤15mol%) 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.X-ray 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.Ab initio 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.