Abstract
Magnesium oxide crystals implanted with ions at doses ranging from to ions/ (ion energy 70, 100, and 150 keV) were studied with the conversion-electron Mössbauer-spectroscopy technique. Supplementary data were obtained using the techniques of Rutherford backscattering and channeling of particles, optical absorption, electron microscopy, and electrical conductivity. It was found that implantation introduces iron in MgO in three charge states: , , and metallic precipitates () with the dominant role of at low doses, at medium doses, and metallic iron clusters at the highest doses. The phase created in a medium range of doses can be compared with the magnesio-wüstite solid solution. The isochronal thermal annealings in air at temperatures between 300 and 700°C gradually cause the oxidation and the nucleation of highly dispersed spinel-like clusters and then, at about 800-900°C, the growth of magnesioferrite particles. In contrast, the heat treatment in vacuum converts all iron into well-diluted in MgO phase. The nature of point defects and their role in annealing processes are discussed on the basis of the optical absorption data. A good correspondence between the results of Mössbauer and channeling data is indicated. The effect of the insulator-conductor transition occurring under iron-ion implantation in MgO and observed by electrical conductivity measurements is explained in terms of the atomistic properties of implanted crystals under study.
- Received 17 February 1983
DOI:https://doi.org/10.1103/PhysRevB.28.1227
©1983 American Physical Society