Microstructure, mechanical, thermal, EPR, and optical properties of MgAl<sub>2sub>O<sub>4sub>:Cr<sup>3+sup> spinel glass-ceramic nanocomposites
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- 作者：A.R. Molla ; C.R. Kesavulu ; R.P.S. Chakradhar ; A. Tarafder ; S.K. Mohanty ; J.L. Rao ; B. Karmakar ; S.K. Biswas
- 关键词：Glass&ndash ; ceramics ; Spinel ; Microstructure ; EPR ; Optical ; Mechanical properties
- 刊名：Journal of Alloys and Compounds
- 出版年：15 January, 2014
- 年：2014
- 卷：583
- 期：Complete
- 页码：498-509
- 全文大小：3192 K
文摘
The mechanical, thermal, and optical properties, along with the microstructure and electron paramagnetic resonance (EPR) spectra, have been studied for MgAl<sub>2sub>O<sub>4sub>:Cr<sup>3+sup> 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 MgAl<sub>2sub>O<sub>4sub> spinel as the only crystalline phase, formed in the heat-treated glass-ceramics. The EPR spectrum of Cr<sup>3+sup> 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 Cr<sup>3+sup> ions caused by the spin-forbidden <sup>2sup>E<sub>gsub> 鈫?#xA0;<sup>4sup>A<sub>2gsub> transition. All the mechanical properties are found to have improved in the glass-ceramics when compared to glasses. A good combination of micro-hardness (鈭?.0 GPa), high fracture toughness (鈭?.0 MPa m<sup>1/2sup>), 3 point flexural strength (鈭?00 MPa) and elastic modulus (鈭?5 GPa) has been obtained for the glass-ceramic samples.