Journal
JOURNAL OF ALLOYS AND COMPOUNDS
Volume 583, Issue -, Pages 498-509Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jallcom.2013.08.122
Keywords
Glass-ceramics; Spinel; Microstructure; EPR; Optical; Mechanical properties
Categories
Funding
- CSIR, Government of India [NWP 0029, ESC 0104]
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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.
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