ELECTRON-PARAMAGNETIC-RESONANCE AND MOSSBAUER-SPECTRA OF IRON IONS INBIZEN POTTERY

Electron paramagnetic resonance (EPR) and Mossbauer spectra of Japanes e traditional Bizen pottery and its constituent clays have been measur ed to study the relationship between the color of pottery surface and the relevant states of iron ions (Fe3+ and Fe2+). Hyperfine signals of Mn2+, presumably in carbonates, and a broad signal at g = 2.0 similar to that of hematite (Fe2O3) were observed for good-quality clay, whil e a signal at g > 9 similar to that of magnetite (Fe3O4) was observed for poor-quality clay. In pottery, the apparent g-factor of g = 4.3 du e to the apparent g-factor of g = 4.3 due to a large orthorhombic dist ortion E (S-x(2)-S-y(2)) and g = 6 due to a large axial field DSz2 wer e observed in addition to the broad signal around g = 2 due to oxidati on of iron into Fe2O3. Subtle change of colors resulted in the change of EPR spectra. Mossbauer spectra indicated that almost all of the iro n ions at the surface of pottery are strongly oxidized into Fe3+ when the pottery is fired in oxidizing atmosphere, while those inside the p ottery and at the surface fired at reducing atmosphere are not strongl y oxidized into Fe3+.