Processing and Optical Properties of Eu-Doped Chloroborate Glass-Ceramic

Mihail Secu,Corina Elisabeta Secu

doi:10.3390/cryst10121101

Abstract

An europium doped BaO–B2O3–BaCl2 chloroborate glass-ceramic containing a BaCl2 nanocrystalline phase was produced by melt-quenching followed by glass crystallization during annealing. Structural and morphological investigations using x-ray diffraction and scanning electron microscopy have shown fvBaCl2 nanocrystals of about tens of nm size accompanied by a smaller amount of the BaB2O4 crystalline phase. Photoluminescence spectra have indicated the reduction of Eu3+ to Eu2+ during processing in air or a reducing atmosphere. The spectra analysis showed the presence of Eu3+ ions in the borate glass matrix, while the Eu2+ were incorporated in both the BaCl2 nanocrystals and glass matrix. Thermoluminescence properties were due to the recombination of F(Cl) centers and Eu2+ related hole centers produced by irradiation within the BaCl2 nanocrystals. The color impression of the samples and the photoluminescence quantum efficiency were influenced by the glass processing.

Highlights

Glass-ceramics are composite materials formed by a nano-crystalline phase dispersed within a glass matrix
The thermogravimetry (TG) curve recorded on the prepared glass sample showed a monotone increase with the temperature, but several peaks were observed on the differential scanning calorimetry (DSC) curve (Figure 1)
Between 525 and 600 ◦ C, we observed a composed exothermic peak Tcr. that was assigned to the glass ceramization associated with the precipitation of BaCl2 and β-BaB2 O4 phases within the glass matrix [11], as was shown by X-ray diffractometry (XRD) analysis

Summary

Introduction

Glass-ceramics are composite materials formed by a nano-crystalline phase dispersed within a glass matrix. Transparent glass-ceramics offer balanced properties between a glassy material and crystals. Most studies have been focused on the preparation and characterization of RE-doped transparent oxyfluoride glass-ceramics containing nanocrystalline fluorides such as PbF2 , CaF2 , BaF2 , LaF3 , NaLaF4 , etc. The thermal stability and chemical advantages of oxide glasses combine with those of the fluoride environment of dopant ions that assures a high luminescence efficiency because of low phonon energies and low non-radiative decay rates. Transparent fluorozirconate-based glass-ceramics containing RE3+ -doped BaCl2 nanocrystals represent new developments in the field, and their crystallization behavior [4,5] and optical properties have been investigated [6]. The synthesis and crystallization properties of barium borate glass-ceramics in the

Objectives

Methods

Results