Hemantha Kumar, G N and Parthasarathy, G and Chakradhar, R P S and Rao, J Lakshmana and Ratnakaram, Y C (2010) Temperature dependence on the electron paramagnetic resonance spectra of natural jasper from Taroko Gorge (Taiwan). Physics and Chemistry of Minerals, 37 (4). pp. 201-208. ISSN 0342-1791

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Abstract

Structural properties of natural jasper from Taroko Gorge (Taiwan) have been investigated by means of powder X-ray diffraction, electron paramagnetic resonance (EPR) and Fourier transform infrared spectroscopic techniques. The EPR spectrum at room temperature exhibits a sharp resonance signal at g = 2.007 and two more resonance signals centered at g a parts per thousand 4.3 and 14.0. The resonance signal at g = 2.007 has been attributed to the E' center and is related to a natural radiation-induced paramagnetic defect. Two more resonance signals centered at g a parts per thousand 4.3 and 14.0 are characteristic of Fe(3+) ions. The EPR spectra recorded at room temperature of jasper samples, heat-treated at temperatures ranging from 473 to 1,473 K exhibit marked temperature dependence. The resonance signal corresponding to E' center disappears at elevated temperatures. A broad, intense resonance signal centered at g a parts per thousand 2.0 appears at elevated temperatures. This resonance signal is a characteristic of Fe(3+) ions, which are present as hematite in the jasper sample. The intensity of the resonance signal becomes dominant at elevated temperatures at a parts per thousand yen873 K, masking g a parts per thousand 4.3 and g a parts per thousand 14.0 resonance signals. The EPR spectra of jasper heat-treated at 673 K have been recorded at temperatures between 123 and 296 K. The population of spin levels (N) has been calculated for the broad g a parts per thousand 2.0 resonance signal. It is found that N decreases with decreasing temperature. The linewidth (Delta H) of g a parts per thousand 2.0 resonance signal of the heat-treated jasper is found to increase with decreasing temperature. This has been attributed to spin-spin interaction of the Fe(3+) ions present in the form of hematite in the studied jasper sample.

Item Type:	Article
Uncontrolled Keywords:	Jasper; Fe(3+); Powder XRD; Electron paramagnetic resonance; Taiwan
Subjects:	Microstructure and Characterization
Divisions:	UNSPECIFIED
Depositing User:	Bidhan Chaudhuri
Date Deposited:	14 Feb 2012 07:12
Last Modified:	14 Feb 2012 07:12
URI:	http://cgcri.csircentral.net/id/eprint/802

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