Hostname: page-component-586b7cd67f-gb8f7 Total loading time: 0 Render date: 2024-11-25T15:23:32.459Z Has data issue: false hasContentIssue false
  • English
  • Français

Origin of Paramagnetic Defect in Single Crystal and Ceramic B4C

Published online by Cambridge University Press:  25 February 2011

E. L. Venturini ,
D. Emin  and
T. L. Aselage
E. L. Venturini
Affiliation:
Sandia National Laboratories, Albuquerque, NM 87185-5800
D. Emin
Affiliation:
Sandia National Laboratories, Albuquerque, NM 87185-5800
T. L. Aselage
Affiliation:
Sandia National Laboratories, Albuquerque, NM 87185-5800
Get access

Abstract

We compare electron spin resonance (ESR) spectra of B4C samples made by three methods. The samples are 1) two ceramics made by hot-pressing boron and carbon powders, 2) a polycrystal made by carbothermic reduction, and 3) a single crystal grown from a palladium metal melt. All samples show remarkably similar spectra between 2 and 100 K. In particular, all samples show a single Lorentzian absorption, a linewidth that decreases with increasing temperature, and an inverse temperature dependence of the integrated intensity. The integrated intensity of the paramagnetic spin signal corresponds to a density of 2×1019/cm2 localized spins. Having a single crystal sample enables us to meaningfully measure the angular dependence of the ESR linewidth. This angular dependence is consistent with the paramagetic centers being unpaired electrons centered on the central carbon atoms of positively charged C-C-C intericosahedral chains. These chains appear to replace 0.5 % of the positively charged C-B-C intericosahedral chains which occur in B4C.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 97: Symposium I – Novel Refractory Semiconductors , 1987 , 57
Copyright
Copyright © Materials Research Society 1987

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

1. Morosin, B., Mullendore, A. W., Emin, D. and Slack, G. A., in Boron-Rich Solids, edited by Emin, D., Aselage, T., Beckel, C. L., Howard, I. A. and Wood, C., AIP Conf. Proc. 140 (Amer. Inst. Phys., New York, 1986), pp. 70–86; H. L. Yakel, Boron-Rich Solids, edited by D. Emin, T. Aselage, C. L. Beckel, I. A. Howard and C. Wood, AIP Conf. Proc. 140 (Amer. Inst. Phys., New York, 1986), pp. 97–108; A. C. Larson, Boron-Rich Solids, edited by D. Emin, T. Aselage, C. L. Beckel, I. A. Howard and C. Wood, AIP Conf. Proc. 140 (Amer. Inst. Phys., New York, 1986), pp. 109–113.Google Scholar
2. Emin, D. and Wood, C., Proc. 18th Intersociety Energy Conversion Conference (Amer. Inst. Chem. Eng., New York, 1983), Vol.1, p. 222.Google Scholar
3. Wood, C. and Emin, D., Phys. Rev. B29, 4582 (1984).Google Scholar
4. Emin, D., in Boron-Rich Solids, edited by Emin, D., Aselage, T. L., Beckel, C. L., Howard, I. A. and Wood, C., AIP Conf. Proc. 140 (Amer. Inst. Phys., New York, 1986), pp. 189–205.Google Scholar
5. Schilfgaarde, M. Van and Harrison, W. A., J. Phys. Chem. Solids 46, 1093 (1985).Google Scholar
6. Azevedo, L. J., Venturini, E. L., Emin, D. and Wood, C., Phys. Rev. B 32, 7970–7972 (1985); L. J. Azevedo, E. L. Venturini, D. Emin and C. Wood, in Boron-Rich Solids, pp. 288–291.Google Scholar
7. Venturini, E. L., Azevedo, L. J., Emin, D. and Wood, C., in Boron-Rich Solids, pp. 292–304. Several references to prior ESR studies of boron carbides are given in the paper.Google Scholar
8. Elsner, N. B., Reynolds, G. H., Norman, J. H. and Shearer, C. H., in Boron-Rich Solids, pp. 59–69.Google Scholar
9. Aselage, T. L., this symposium proceedings.Google Scholar
10. Poole, C. P. Jr, Electron Spin Resonance, A Comprehensive Treatise on Experimental Techniques, (Interscience, New York, 1967), pp. 820–825.Google Scholar
11. Green, T. A. and Emin, D., to be published.Google Scholar
12. Vlasova, M. V., Kakazey, N. G., Kosolapova, T. Y., Makarenko, G. N., Marek, E. V., Uskokovic, D. and Ristic, M. M., J. Mater. Sci. 15, 1041 (1980).Google Scholar
13. Bandyopadhyay, A. K., Beuneu, F., Zuppiroli, L. and Beauvy, M., J. Phys. Chem. Solids 45, 207 (1984).Google Scholar
14. Bodnaruk, N. I., Vlasova, M. V., Kakazei, N. G. and Kislyi, P. S., Zh. Prik. Spektr. 31, 154 (1979) (translation: J. Appl. Spectr. 31, 920 (1980)).Google Scholar