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EPR spectra of a new radiation-induced paramagnetic centre in kaolins

Published online by Cambridge University Press:  02 January 2018

Bernard A. Goodman ,
Niramon Worasith  and
Wen Deng
Bernard A. Goodman*
Affiliation:
College of Physical Science & Engineering, Guangxi University, Nanning, 530004 Guangxi, China State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi University, Nanning, 530004 Guangxi, China
Niramon Worasith
Affiliation:
Department of Chemistry, Faculty of Science and Technology, Rajamangala University of Technology Krungthep, 2 Nang Lin Chi Road, Soi Suan Plu, Sathorn, Bangkok, Thailand
Wen Deng
Affiliation:
College of Physical Science & Engineering, Guangxi University, Nanning, 530004 Guangxi, China
*
*E-mail: bernard_a_goodman@yahoo.com
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Abstract

The EPR spectrum of a previously unreported paramagnetic centre formed in kaolin minerals by exposure to γ radiation is described. This centre, which is referred to here as the ‘C-centre’, was seen initially during an investigation of the radiation dose response of the EPR signal in the natural Lampang kaolin from northern Thailand, and its EPR properties are now presented for a purified sample from this material. They suggest a paramagnetic centre with rhombic symmetry based on O− associated with a single 27Al atom. Computer simulations suggest spin Hamiltonian parameters of g1 = 1.976, g3 = 2.0417 and A(27Al) = 2.10 mT, with g2 ≈ 2.01. This C-centre was also seen as a minor radiationinduced component in both crude and purified Ranong kaolin samples, along with a stronger signal from the B-centre radical. It seems to be associated with the kaolinite component, but was lost on annealing to 300°C after which only the signal from the A-centre was visible.

Keywords

kaolinitefree radicalγ radiation27Al hyperfine structure
Type
Research Article
Information
Clay Minerals , Volume 51 , Issue 5 , December 2016 , pp. 707 - 714
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2016

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