Crystallization and visible-near-infrared luminescence of Bi-doped gehlenite glass.

M Majerová,J Kraxner,R Klement,A Prnová,E Bruneel,D Galusek

doi:10.1098/rsos.181667

Abstract

Gehlenite glass microspheres, doped with a different concentration of Bi3+ ions (0.5, 1, 3 mol%), were prepared by a combination of solid-state reaction followed by flame synthesis. The prepared glass microspheres were characterized from the point of view of surface morphology, phase composition, thermal and photoluminescence (PL) properties by optical and scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and PL spectroscopy. The closer inspection of glass microsphere surface by SEM confirmed a smooth surface. This was further verified by XRD. The basic thermal characteristics of prepared glasses, i.e. Tg (glass transition temperature), Tx (onset of crystallization peak temperature), Tf (temperature of the inflection point of the crystallization peak) and Tp (maximum of crystallization peak temperature), were estimated from the DSC records. High-temperature XRD experiments in the temperature interval range 600–1100°C were also performed. The PL emission properties of prepared glasses and their polycrystalline analogues (glass crystallized at 1000°C for 10 h) were studied in the visible and near-infrared (NIR) spectral range. When excited at 300 nm, the glasses, as well as their polycrystalline analogues, exhibit broad emission in the visible spectral range from 350 to 650 nm centred at about 410–450 nm, corresponding to Bi3+ luminescence centres. The emission intensity of polycrystalline samples was found to be at least 30 times higher than the emission of their glass analogues. In addition, a weak emission band was observed around 775 nm under 300 nm excitation. This band was attributed to the presence of a minor amount of Bi2+ species in prepared samples. In the NIR spectral range, the broad band emission was observed in the spectral range of 1200–1600 nm with the maxima at 1350 nm. The chemistry of Bi and its oxidation state equilibrium in glasses and polycrystalline matrices is discussed in detail.

Highlights

Since the 1990s, compounds with melilite structure have been intensively studied due to their interesting electrochemical [1], magnetic [2,3,4], luminescence [5 –7] and structural properties [8,9,10]
We investigated the luminescence properties of Bi2O3-doped gehlenite glass microspheres prepared by flame synthesis and studied the influence of crystallization of the glass on the luminescence in visible and NIR wavelength range
scanning electron microscopy (SEM) examination of polished cross sections confirmed the amorphous character of prepared glass microspheres; no morphological features indicating the presence of crystalline phases were observed

Summary

Introduction

Since the 1990s, compounds with melilite structure have been intensively studied due to their interesting electrochemical [1], magnetic [2,3,4], luminescence [5 –7] and structural properties [8,9,10]. The structure of melilite compounds, which belong to a sorosilicate group of minerals, was first determined by Warren [11]. The structure has a tetragonal symmetry space group P-421m and consists of BC2O7 layers parallel to (0 0 1) with corner-sharing BO4 and CO4 tetrahedra. The A cations are placed between these layers in distorted square antiprisms of oxygen atoms. Owing to their tetragonal and non-centrosymmetric crystal structure, lanthanides or transition metals can be accepted as dopants by the melilites [3]

Methods

Results

Conclusion