TY - JOUR
T1 - High temperature calorimetric studies of the heat of solution of La2O3 in silicate liquids
AU - Wilding, Martin C.
AU - Navrotsky, Alexandra
N1 - Funding Information:
This research has been supported by the National Science Foundation (grant EAR 94-17945). In addition, later stages of this work and the essential infrastructure for the calorimetry laboratory has been provided by the Center for High Pressure Research (CHiPR), an NSF Science and Technology Center. We thank Bennett, Topor and Norton for technical assistance. Electron microprobe facilities at the Princeton Materials Institute are supported by NSF grant DMR 9400362. Vicenzi provided valuable assistance during microprobe analysis. We would also like to thank two anonymous reviewers for their constructive comments.
PY - 2000/3
Y1 - 2000/3
N2 - High temperature calorimetry at 1760 K has been used to measure the heat of solution of La2O3 in a series of simple alkali and alkaline earth silicate liquids. The heat of solution in these solvents is strongly exothermic and varies as a function of liquid composition. However, the variation of the heat of solution does not follow simple trends related to cation size or charge and varies little with La2O3 concentration. The variation of heat of solution with composition of the liquid reflects the ability of La(III) to perturb the transient silicate framework and compete with other cations for oxygen. This complex pattern of melt energetics is consistent with recent spectroscopic measurements which suggest extreme perturbation of the silicate framework by La(III), sufficient to isolate oxygen from silicon. This interpretation suggests the presence of phase-ordered regions rich in La(III) consistent with incipient liquid-liquid immiscibility suggested by previous calorimetric studies. Within error the heat capacity of La-bearing silicate liquids is the same over the super-cooled liquid range as in the stable liquid, with no evidence for the large heat capacities associated with melt restructuring. Thus the energetics of the liquid are dominated by the exothermic reactions which form La-clusters and these phase-ordered regions do not dissociate as temperature increases up to 1760 K.
AB - High temperature calorimetry at 1760 K has been used to measure the heat of solution of La2O3 in a series of simple alkali and alkaline earth silicate liquids. The heat of solution in these solvents is strongly exothermic and varies as a function of liquid composition. However, the variation of the heat of solution does not follow simple trends related to cation size or charge and varies little with La2O3 concentration. The variation of heat of solution with composition of the liquid reflects the ability of La(III) to perturb the transient silicate framework and compete with other cations for oxygen. This complex pattern of melt energetics is consistent with recent spectroscopic measurements which suggest extreme perturbation of the silicate framework by La(III), sufficient to isolate oxygen from silicon. This interpretation suggests the presence of phase-ordered regions rich in La(III) consistent with incipient liquid-liquid immiscibility suggested by previous calorimetric studies. Within error the heat capacity of La-bearing silicate liquids is the same over the super-cooled liquid range as in the stable liquid, with no evidence for the large heat capacities associated with melt restructuring. Thus the energetics of the liquid are dominated by the exothermic reactions which form La-clusters and these phase-ordered regions do not dissociate as temperature increases up to 1760 K.
UR - http://www.scopus.com/inward/record.url?scp=0033897048&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0033897048&partnerID=8YFLogxK
U2 - 10.1016/S0022-3093(00)00007-7
DO - 10.1016/S0022-3093(00)00007-7
M3 - Article
AN - SCOPUS:0033897048
SN - 0022-3093
VL - 265
SP - 238
EP - 251
JO - Journal of Non-Crystalline Solids
JF - Journal of Non-Crystalline Solids
IS - 3
ER -