Double hysteresis loops and temperature–field phase diagram in Pb(Mg_1/3Nb_2/3)O₃–29.5%PbTiO₃

Polarization–electric field (p–E) hysteresis loops in 70.5%Pb(Mg1/3Nb2/3)O3–29.5%PbTiO3 (PMN–29.5%PT) have been observed in the temperature range between 40 °C and 200 °C. In temperature range above the phase transition temperature under zero biasing field, the ferroelectric critical endpoint (CEP) in the temperature–field phase diagram in the dc biasing field applied along the [001]c direction (in the cubic coordinate) has been found at 138.5 °C and 1.2 kV cm−1, while the temperature dependence of the spontaneous polarization has been clarified in the ferroelectric phase. Our experimental results of the ferroelectric CEP and spontaneous polarization in PMN–29.5%PT have been discussed on the basis of the Landau-type phenomenological theory.