Cation Distribution, Short-Range Order and Small Polaron Hopping Conduction in Nickel Manganites, from a Neutron Diffraction Study
✍ Scribed by E. Elbadraoui; J. L. Baudour; C. Leroux; S. Fritsch; F. Bouree; B. Gillot; A. Rousset
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 238 KB
- Volume
- 212
- Category
- Article
- ISSN
- 0370-1972
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✦ Synopsis
By means of neutron diffraction, a study has been made of the variation of the cationic distribution and short-range order in nickel-manganite ceramics Ni 0.8 Mn 2.2 O 4 , in relation with their thermal history. The thermal treatment of metallization which is an annealing at 850 C followed by a quenching, induces a partial migration of Ni 2+ ions from octahedral B to tetrahedral A sites of the cubic spinel structure and a decrease of the short-range order between nickel and manganese atoms on the B sites. These two effects increase the probability of the hopping of electrons from octahedral-site Mn 3+ to octahedral-site Mn 4+ and provide the major mechanism for the electrical conductivity increase associated with the thermal treatment of metallization of ceramics.
La diffraction neutronique a permis d'e  tudier la variation de la distribution cationique et de l'ordre a Á courte distance dans les ce  ramiques de manganite de nickel Ni 0,8 Mn 2,2 O 4 , en relation avec leur histoire thermique. Le traitement thermique de me  tallisation, un recuit a Á 850 C suivi d'une trempe, provoque une migration partielle des ions Ni 2+ des sites octae  driques B vers les sites te  trae  driques A de la structure cubique spinelle et une diminution de l'ordre a Á courte distance entre les atomes de nickel et de mangane Á se sur les sites B. Ces deux effets augmentent la probabilite  des sauts d'e  lectrons entre les ions Mn 3+ et les ions Mn 4+ en sites B et rendent ainsi compte en grande partie de l'augmentation de conductivite  e  lectrique associe  e au traitement thermique de me  tallisation des ce  ramiques.