Study of Na₂O-SiO₂-Fe₂O₂-Y₂O₃ glass by Mossbauer and EPR spectroscopy

Abstract

Mössbauer, EPR and magnetization experiments have been carried out on the glass composition Na₂O-SiO₂-Fe₂O₂-Y₂O₃ in which yttrium iron garnet (YIG) can be precipitated by suitable heat-treatment. The measurements have been carried out on the as-quenched sample as well as samples heat-treated for 4 h at 400, 500, 600, 650, 700, 750, 810 and 850 C. Mössbauer spectra from the as-quenched sample as well as the first six samples showed a quadrupole splitting while the last two samples, as well as the sample heat-treated (i) by a two-stage process at 600 C and then at 750 C for 4 h each, and (ii) at 700 C for 40 h, showed a hyperfine as well as quadrupole splitting. The behaviour of the isomer shift (IS) and quadrupole splitting (δE) with the heat-treatment temperature show significant changes at the glass transition and crystallization temperatures. The Mössbauer data have been found consistent with optical and electron micrographs which show a large variation in particle size of the precipitated magnetic phase. This has been further correlated with EPR and magnetization data.