Low-temperature heat capacities and Raman spectra of negative thermal expansion compounds and
- 20 June 2002
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review B
- Vol. 66 (1), 014301
- https://doi.org/10.1103/physrevb.66.014301
Abstract
Heat capacities of and were precisely measured between 1.8 and 330 K. Heat-capacity curves of and are very similar to each other. The heat capacity of at low temperature is larger than that of due to atomic mass effect, but both heat capacities cross around 220 K. Raman spectra of and were recorded at room temperature. Frequency distributions of lattice vibrations were estimated through an analysis of the heat capacities for and It is found that the difference in the frequency distributions between and arises from the different atomic mass and bond strength, and causes the different temperature dependence of the heat capacities. The properties of the optical-phonon modes with a large negative mode-Grüneisen parameter are discussed.
Keywords
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