Study of the Ferroelastic Phase Transition of TIH2PO4 Acoustic Phonon Softening

Article abstract of DOI:10.1143/JPSJ.60.188

Elastic, thermal and dielectric measurements of TIH₂PO ₄ were carried out in a temperature range covering the upper phase transition point at 357 K. The specific heat shows a λ-type anomaly associated with the upper phase transition of second order and yields the transition entropy ΔS= 1.46 J/mol-K. The elastic stiffness c₅₅ among c_u(i= 1, 2, ..., 6) determined from the ultrasonic velocity data at a frequency of 10 MHz shows a large anomaly with a tendency to approach zero in value at the upper phase transition point. It was shown that the upper, ferroelastic phase transition is caused by an instability of the B_2g transverse acoustic mode, and the elastic, thermal and dielectric behaviours near the ferroelastic phase transition point can be reasonably explained by a phenomenological theory.

Full text of DOI:10.1143/JPSJ.60.188

J. Phys. Soc. Jpn.
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J. Phys. Soc. Jpn.
Downloaded from journals.jps.jp by University of Liverpool on 11/01/17

J. Phys. Soc. Jpn.
Downloaded from journals.jps.jp by University of Liverpool on 11/01/17

J. Phys. Soc. Jpn.
Downloaded from journals.jps.jp by University of Liverpool on 11/01/17

J. Phys. Soc. Jpn.
Downloaded from journals.jps.jp by University of Liverpool on 11/01/17

J. Phys. Soc. Jpn.
Downloaded from journals.jps.jp by University of Liverpool on 11/01/17

J. Phys. Soc. Jpn.
Downloaded from journals.jps.jp by University of Liverpool on 11/01/17

J. Phys. Soc. Jpn.
Downloaded from journals.jps.jp by University of Liverpool on 11/01/17