抄録
The crystallographic features of the ferroelectric tetragonal (FT) state in (1 − x)Pb(Sc1/2Nb1/2)O3–xPbTiO3 (PSN–xPT) were investigated between 300 and 700 K, primarily using transmission electron microscopy (TEM) with the help of the failure of Friedel’s law in electron diffraction. The ferroelectric state for 0.60 ≤ x < 1.0, which has been recognized as the normal FT state thus far, was found to have MC-type monoclinic symmetry with ⟨201⟩C polarization vectors in the {100}C planes. Notably, the ferroelectric MC state (FMC) was characterized by pseudo 90 and 180° domain structures, in which the polarization rotates slightly from the ⟨001⟩C direction of the FT state. In addition, in situ TEM observation during heating and permittivity measurement revealed that the (FMC → FT) transition occurred at below TC for 0.60 ≤ x < 1.0. The FT/FMC phase boundary, which is nearly perpendicular to the temperature axis, was therefore present at approximately 560 K.
