The temperature-pressure phase diagram of BaTiO 3 has been determined by means of a dielectric measurement. All successive phase transition temperatures decrease with increasing pressure with critical index f 1, in the classical limit, and f 2, in the quantum limit. The dielectric behavior close to the quantum region agrees with the quantum theoretical prediction. In BaTiO 3 the crossover region from the classical limit to the quantum one is observed in the range of pressure 4 to 8 GPa and temperature 0 to 200 K.
The Raman spectrum of SrTiO, as a function of hydrostatic pressure up to 15 GPa was studied at room temperature. The structural phase transition of cubic to tetragonal phase occurred at p c = 6.4 GPa. In the high pressure phase four first-order Raman active modes, i.e. two soft A, and E, modes and two high frequency E, and B, modes were observed. The second-order Raman modes decreased in intensity with increase of pressure and disappeared at 13 GPa. The high frequency E, and B, modes increased in intensity with pressure. The soft A, and E, mode frequencies were analysed with the expression w2 = w$(p/p, -1) with w,, = 82.4 cm-l for A, and 33.4 cm-' for E,. The result was discussed on the basis of the phenomenological theory.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.