Hostname: page-component-7dd5485656-hw7sx Total loading time: 0 Render date: 2025-10-30T15:10:40.474Z Has data issue: false hasContentIssue false
  • English
  • Français

Decomposition of NiMn2O4 spinels

Published online by Cambridge University Press:  31 January 2011

G. D. C. Csete de Györgyfalva  and
I. M. Reaney
G. D. C. Csete de Györgyfalva
Affiliation:
Department of Engineering Materials, Sir Robert Hadfield Building, Mappin St. University of Sheffield, Sheffield, S1 3JD, United Kingdom
I. M. Reaney
Affiliation:
Department of Engineering Materials, Sir Robert Hadfield Building, Mappin St. University of Sheffield, Sheffield, S1 3JD, United Kingdom
Get access

Abstract

Thermal analysis and x-ray diffraction have confirmed that single-phase, cubic-spinel-structured NiMn2O4 (2:1 Mn2O3:NiO) begins to decompose into a rocksalt and a second spinel-structured phase above 907 °C. The decomposition product in samples air-quenched from 900 and 1200 °C was therefore investigated using transmission electron microscopy. Samples quenched from 900 °C (below decomposition temperature) did not show the expected single-phase microstructure, but instead grains contained nanoregions of a lenticular fringe contrast. Samples quenched from 1050 to 1200 °C were generally composed of Mn-rich spinel grains in addition to grains containing Mn-rich spinel precipitates (30–50 nm) surrounded by a Ni-rich rocksalt matrix. As temperature increased, the spinel grains and precipitates became clearly tetragonal, exhibiting a ferroelastic domain structure arising from a cooperative Jahn–Teller distortion. A decomposition mechanism based on the degree of inversion is proposed to explain these microstructures. Slow cooling samples from 1250 °C resulted in partial recomposition, leading to a microstructure principally composed of cubic spinel and regions of much smaller spinel structured precipitates (50–120 nm) in a rocksalt structured matrix. The slow-cooled samples showed a larger increase in resistance over time than single-phase samples did when held at 400 °C. X-ray diffraction measurements carried out before and after electrical characterization showed a reduction in the amount of rocksalt structured material present in slow-cooled samples.

Information

Type
Articles
Information
Journal of Materials Research , Volume 18 , Issue 6 , June 2003 , pp. 1301 - 1308
Copyright
Copyright © Materials Research Society 2003

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.)

Article purchase

Temporarily unavailable

References

REFERENCES

1.Larson, E.G., Arnott, R.J., and Wickham, D.G., J. Phys. Chem. Solids 23, 1771 (1962).Google Scholar
2.Gillot, B., Kharroubi, M., Metz, R., Legros, R., and Rousset, A., Solid State Ionics 44, 3–4, 275 (1991).Google Scholar
3.Shriver, D.F., Atkins, P.W., and Langford, C.H., Inorganic Chemistry (Oxford University Press, Oxford, U.K., 1992).Google Scholar
4.Couderc, J.J., Fritsch, S., Brieu, M., Vanderschaeve, G., Fagot, M., and Rousset, A., Philos. Mag. B 70, 1077 (1994).CrossRefGoogle Scholar
5.Metzmacher, C., Reaney, I.M., and Groen, W., Phys. Status Solidi A 181, 369 (2000).3.0.CO;2-5>CrossRefGoogle Scholar
6.Fishman, A.Ya., Ivanov, M.A., Mitrofanov, V.Ya., and Shemyakov, A.A., Phys. Status Solidi B 160, 153 (1990).Google Scholar
7.Brabers, V.A.M. and Terhell, J.C.J., Phys. Status Solidi A 6, 325 (1982).CrossRefGoogle Scholar
8.Verwey, E.J., Haayman, P.W., Romeyn, F.C., and Oosterhout, G.W. van, Philips Res. Rep. 5, 173 (1950).Google Scholar
9.Dorris, S.E. and Mason, T.O., J. Am. Ceram. Soc. 71, 379 (1988).Google Scholar
10.Groen, W.A., Zaspalis, V., and Schuurman, S., J. Mater. Sci. Lett. 18(15), 1233 (1999).CrossRefGoogle Scholar
11.Boucher, B., Buhl, R., and Perrin, M., Acta Crystallogr. B 25, 2326 (1969).CrossRefGoogle Scholar
12.Feltz, A., Toepfer, J., and Schirrmeister, F., J. Eur. Ceram. Soc. 9, 187 (1992).Google Scholar
13.Wickham, D.G., J. Inorg. Nucl. Chem. 26, 1369 (1963).Google Scholar
14.Jung, J., Topfer, J., Murbe, J., and Feltz, A., J. Eur. Cer. Soc. 6, 351 (1990).Google Scholar
15.Gyorgyfalva, G.D.C. Csete de, Reaney, I.M., Metzmacher, C., and Groen, W., Proc. EMAG 99. (Inst. Phys. Conf. Series 161, London, U.K., 1999), pp. 529–532.Google Scholar
16.Gyo¨rgyfalva, G.D.C. Csete de, Nolte, A.N., and Reaney, I.M., J. Eur. Ceram. Soc. 19, 857 (1999).CrossRefGoogle Scholar
17.Schmalzried, H., Solid State Reactions, 2nd ed. (Verlag Chemie, Weinheim, Germany, 1981).Google Scholar