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Structural investigation of MnO-B2O3-PbO-Ag2O glass system by EPR spectroscopy

V. TIMAR1, I. ARDELEAN1,*

Affiliation

  1. Faculty of Physics, Babes-Bolyai University, 400084, Cluj-Napoca, Romania

Abstract

Glasses of the xMnO·(100-x)[3B2O3·(1-y)PbO·yAg2O] systems, with 0 ≤ x ≤ 20 mol% and y = 0.1, 0.3, 0.5 were prepared and investigated by means of electron paramagnetic resonance (EPR) measurements. The local order in diamagnetic vitreous matrices may be revealed by the Mn2+ paramagnetic ions used in EPR experiments. The concentration range in which homogeneous glasses systems are formed (0 ≤ x ≤ 20 mol%) is not influenced on particular values of y. In each systems corresponding a particular value of y, the effect of increasing the MnO content in the samples was investigated. The EPR absorption spectra of all investigated samples exhibit two resonance signals that are characteristic for the Mn2+ (3d5; 5 26S / ) ions, centered at geff ≅ 4.3 and geff ≅ 2.0. The relative intensity of these resonance lines depends on the MnO content in the samples, indicated the various distribution of the Mn2+ ions on different structural units of vitreous matrices. For x ≤ 5 mol%, geff ≅ 2.0 resonance line has a resolved hyperfine structure (hfs) characteristic for isolated Mn2+ ions. Hfs is superposed over the wide line, given by dipolar interactions between manganese ions. For 5 < x ≤ 20 mol% concentration range, the resonance line from geff ≅ 2.0 not present hfs, indicating the structural modification in Mn2+ vicinity, gradually increasing of dipolar interactions and the appearance in small proportion of the super-exchange magnetic interactions (x > 1 mol%). The resonance lines centered at geff ≅ 4.3 appear in the whole concentration range, have the small intensity, not present hfs and is attributed to isolated Mn2+ ions disposed in octahedral symmetric sites slightly tetragonally distorted. When increase the Ag2O content in glasses matrices, the shape of EPR spectra is little modified. In addition, it observed a similitude concerning the way of variation from the characteristic parameters of resonance lines (line intensity and linewidth)..

Keywords

Silver-lead-borate glasses, Manganese ions, Local structure, EPR.

Submitted at: Nov. 1, 2008
Accepted at: Dec. 10, 2008

Citation

V. TIMAR, I. ARDELEAN, Structural investigation of MnO-B2O3-PbO-Ag2O glass system by EPR spectroscopy, Journal of Optoelectronics and Advanced Materials Vol. 10, Iss. 12, pp. 3212-3216 (2008)