The heat capacities of thermomiotic ScF3 and ScF3–YF3 solid solutions
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Scandium trifluoride (ScF3) exists in a cubic ReO3 structure that exhibits negative thermal expansion from 10 to 1100 K, while substituted Sc1−x Y x F3 materials display the same behavior at room temperature but transition into positive thermal expansion rhombohedral phases upon cooling. We have measured the heat capacity of ScF3 from 0.4 to 390 K and found no evidence of a phase transition, but do find that its low-temperature heat capacity is anomalously high. The heat capacities of substituted Sc1−x Y x F3 materials are also reported and show evidence of the cubic-rhombohedral phase transition for x ≥ 0.1 and smaller anomalies in the low-temperature heat capacity of the positive thermal expansion rhombohedral phases. To aid in interpretation of these results, the heat capacity of ScF3 was calculated from its phononic structure using density functional theory.
KeywordsHeat Capacity Molar Heat Capacity Rhombohedral Phasis Negative Thermal Expansion Phonon Dispersion Relation
This study was supported by the Natural Sciences and Engineering Research Council of Canada, the Sumner Foundation, and the Canada Foundation for Innovation, the Atlantic Innovation Fund and other partners that fund the Facilities for Materials Characterization managed by the Institute for Research in Materials at Dalhousie University.
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