Abstract :
The liquidus temperature of spinel (AB2O4) crystals frequently limits the waste loading of
vitrified nuclear waste. In other studies, glass structure-spinel liquidus temperature
relationships were discovered for the non-spinel forming cations in glass, but no such
relationship was identified for the spinel-forming metal-ions. In this paper, coefficients from
an empirical first order mixture model describing spinel liquidus temperature were
correlated with the octahedral site preference energy (OSPE) of the spinel-forming metal
ions. The OSPE was calculated using approximations of glass and spinel structure made by
extrapolating from data on similar glasses and spinels. A literature review indicated that
Cr(III), Ni(II), and Fe(II) are most likely to be in the octahedral sites in spinel, Mn(II) in the
tetrahedral site, and that Fe(III) will be common in both sites. These assignments were used
as starting assumptions to calculate the OPSE for each metal ion. A strong correlation
between the OSPE and the liquidus temperature coefficients of spinel-forming metal ions
was observed. Further correlations determined that the Crystal Field Stabilization Energy
was the most important portion of the OSPE for these spinels. These results indicate that
the thermodynamic properties of spinel could be predicted based on assumptions of spinel
structure, underpinned by fundamental properties, when scaled empirically.
C 2005 Springer Science + Business Media, Inc.
