Molla, Atiar Rahaman and Kesavulu, C R and Chakradhar, R P S and Tarafder, Anal and Mohanty, S K and Rao, J L and Karmakar, Basudeb and Biswas, S K (2014) Microstructure, mechanical, thermal, EPR, and optical properties of MgAl2O4:Cr3+ spinel glass-ceramic nanocomposites. Journal of Alloys and Compounds, 583. pp. 498-509. ISSN 0925-8388

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Abstract

The mechanical, thermal, and optical properties, along with the microstructure and electron paramagnetic resonance (EPR) spectra, have been studied for MgAl2O4:Cr3+ spinel glass and glass-ceramics. The activation energy of the crystallization has been estimated from the differential scanning calorimetry (DSC) study using different models and is found to vary within 255-270 kJ/mol for the un-doped precursor glass. The microstructure of the glass-ceramics has been characterized using field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The TEM images demonstrate the presence of cubic crystals in the glass-ceramics of uniform size 10-15 nm. X-ray diffraction (XRD) and Fourier-transform infrared (FT-IR) spectroscopy reveal the presence of MgAl2O4 spinel as the only crystalline phase, formed in the heat-treated glass-ceramics. The EPR spectrum of Cr3+ doped glass sample exhibits a broad resonance signal with effective g = 1.97 whereas in glass-ceramic sample an additional weak resonance signal is observed at g = 3.83. The excitation spectrum exhibits two bands in the visible region. The emission spectrum exhibits an intense red emission at 690 nm which is characteristic of Cr3+ ions caused by the spin-forbidden E-2(g) -> (4)A(2g) transition. All the mechanical properties are found to have improved in the glass-ceramics when compared to glasses. A good combination of micro-hardness (similar to 6.0 GPa), high fracture toughness (similar to 5.0 MPa m(1/2)), 3 point flexural strength (similar to 100 MPa) and elastic modulus (similar to 55 GPa) has been obtained for the glass-ceramic samples. (C) 2013 Elsevier B. V. All rights reserved.

Item Type:	Article
Subjects:	Engineering Materials
Divisions:	Glass
Depositing User:	Bidhan Chaudhuri
Date Deposited:	16 Dec 2014 09:18
Last Modified:	16 Dec 2014 09:18
URI:	http://cgcri.csircentral.net/id/eprint/2644

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