Structural and Thermodynamic Variation in Nickel Aluminate Spinel

Krzysztof Mocala, Alexandra Navrotsky

Research output: Contribution to journalArticlepeer-review

49 Scopus citations

Abstract

New structural and calorimetric data for samples of NiAl2O4 quenched from 600° to 1560°C are presented The spinel remains stoichiometric for all heat treatments. Based on the refinement of X‐ray powder patterns, it is shown that the degree of disorder, defined as the mole fraction of tetrahedral sites occupied by Al3+, changes from x = 0.82 at 600°C to 0.78 at 1560°C. Simultaneously, the lattice parameter and enthalpy vary in a complex manner with quench temperature. The largest lattice parameter (0.80500 ± 0.00004 nm) and most exothermic enthalpy of annealing (heat released when sample is equilibrated at 780°C; ‐10.1 kJ/mol) occur for the sample quenched from 1100°C. A linear correlation exists between the heat of annealing and the lattice parameter. The results have been interpreted as a superposition of at least two effects: (1) the disordering of Ni2+ and Al3+ ions between octahedral (16d) and tetrahedral (8a) sites and (2) a second process, which may be a small amount of the disordering of ions into the usually empty (16c) sites.

Original languageEnglish (US)
Pages (from-to)826-832
Number of pages7
JournalJournal of the American Ceramic Society
Volume72
Issue number5
DOIs
StatePublished - May 1989
Externally publishedYes

Keywords

  • aluminates
  • heat treatment
  • nickel
  • spinels
  • thermodynamics

ASJC Scopus subject areas

  • Ceramics and Composites
  • Materials Chemistry

Fingerprint Dive into the research topics of 'Structural and Thermodynamic Variation in Nickel Aluminate Spinel'. Together they form a unique fingerprint.

Cite this