Low-temperature heat capacities and Raman spectra of negative thermal expansion compounds ZrW 2 O 8 and HfW 2 O 8
Low-temperature heat capacities and Raman spectra of negative thermal expansion compounds ZrW 2 O...
Yamamura, Yasuhisa ; Nakajima, Noriyuki ; Tsuji, Toshihide ; Koyano, Mikio ; Iwasa, Yoshihiro ; Katayama, Shin’ichi
2002-07-01 00:00:00
Heat capacities of ZrW 2 O 8 and HfW 2 O 8 were precisely measured between 1.8 and 330 K. Heat-capacity curves of ZrW 2 O 8 and HfW 2 O 8 are very similar to each other. The heat capacity of HfW 2 O 8 at low temperature is larger than that of ZrW 2 O 8 due to atomic mass effect, but both heat capacities cross around 220 K. Raman spectra of ZrW 2 O 8 and HfW 2 O 8 were recorded at room temperature. Frequency distributions of lattice vibrations were estimated through an analysis of the heat capacities for ZrW 2 O 8 and HfW 2 O 8 . It is found that the difference in the frequency distributions between ZrW 2 O 8 and HfW 2 O 8 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.
http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.pngPhysical Review BAmerican Physical Society (APS)http://www.deepdyve.com/lp/american-physical-society-aps/low-temperature-heat-capacities-and-raman-spectra-of-negative-thermal-f0vUTrF6yq
Low-temperature heat capacities and Raman spectra of negative thermal expansion compounds ZrW 2 O 8 and HfW 2 O 8
Heat capacities of ZrW 2 O 8 and HfW 2 O 8 were precisely measured between 1.8 and 330 K. Heat-capacity curves of ZrW 2 O 8 and HfW 2 O 8 are very similar to each other. The heat capacity of HfW 2 O 8 at low temperature is larger than that of ZrW 2 O 8 due to atomic mass effect, but both heat capacities cross around 220 K. Raman spectra of ZrW 2 O 8 and HfW 2 O 8 were recorded at room temperature. Frequency distributions of lattice vibrations were estimated through an analysis of the heat capacities for ZrW 2 O 8 and HfW 2 O 8 . It is found that the difference in the frequency distributions between ZrW 2 O 8 and HfW 2 O 8 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.
Journal
Physical Review B
– American Physical Society (APS)
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