Surface energy and thermodynamic stability of γ-alumina: Effect of dopants and water

Ricardo H.R. Castro, Sergey V. Ushakov, Leon Gengembre, Douglas Gouvêa, Alexandra Navrotsky

Research output: Contribution to journalArticlepeer-review

91 Scopus citations


Retaining large surface areas in alumina powders during high-temperature annealing is a major challenge in applications as catalyst supports and ceramic precursors. This is because the alumina surface area drastically decreases with transformation from the γ modification (defect spinel structure) into the a modification (corundum structure). The objective of this work is to show the thermodynamic basis of using additives, such as Zr and Mg, to control the γ-Al 2O 3 surface and bulk energetics and to manipulate the transformation temperature and surface area. These additives are observed to change the pattern of phase transformation and densification. Direct measurements of heats of solution in a lead borate melt of pure and doped alumina as a function of surface area enabled us to experimentally derive trends in the surface energies of hydroxylated surfaces. Accounting for heats of water adsorption measured on pure and doped alumina surfaces allowed us to delineate the thermodynamic effects of hydration on surface energies. Zr-doped γ-alumina showed a higher energy of the hydroxylated surface than did pure γ-alumina but showed a lower energy of the anhydrous surface. Mg addition does not change surface energies significantly but decreases the energetic instability of the bulk γ phase.

Original languageEnglish (US)
Pages (from-to)1867-1872
Number of pages6
JournalChemistry of Materials
Issue number7
StatePublished - Apr 4 2006
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry


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