N.M.R. and magnetic study (E.P.R. and magnetization) of BaOB 2O 3SiO 2 glasses containing titanium ions

Abstract

The structure of the magnetic ions in oxide glasses is usually indirectly inferred from the magnetic properties and magnetic interactions between the ions involved. These measurements include dc and ac susceptibility, EPR, Mossbauer spectroscopy, etc. In this work we have combined low temperature dc magnetization and EPR measurements with NMR structural studies on the host glass constituents to obtain more detailed description of the glass structure. NMR measurements, using the B 11, Ba 137, constituent nuclei have been made on two host glasses, Na 2OB 2O 3SiO 2 and BaOB 2O 3SiO 2, containing various concentrations of titanium ions. The concentration of Ti (as TiO 2) varied from 0–10 mole %, the vcr [Ti +3] [Ti total] range between 0 and 0.8 In addition, low field dc magnetization measurements were carried out at liquid helium temperatures, and x-band EPR spectra obtained over wide temperature ranges. Selected examples of the various behaviors are shown. The most striking result is the extreme sensitivity of the three-fold coordinated B and the Ba resonances to the incorporation of titanium into the glass. The magnetic measurements indicate that at the same time, the titanium ions are acting together in either pairs or larger structures. We suggest that there is a synergistic interaction between the modifier ions (Ba +2), the titanium ions, and the non-bridging oxygens which results in their accumulation in micro-heterogeneities. These microheterogeneities we suggest, surround islands of more continuous networks involving the four coordinated boron. This micro-inhomogeneous glass structure is discussed briefly in relation to dc electrical conduction.