PHASE-DIAGRAM OF BATIO3

The temperature-pressure phase diagram of BaTiO3 has been determined b y means of a dielectric measurement. All successive phase transition t emperatures decrease with increasing pressure with critical index phi = 1, in the classical limit, and phi = 2, in the quantum limit. The di electric behavior close to the quantum region agrees with the quantum theoretical prediction. In BaTiO3 the crossover region from the classi cal limit to the quantum one is observed in the range of pressure 4 to 8 GPa and temperature 0 to 200 K.