Reconsideration of the morphotropic phase boundary - the order of the ferroelectric phase transition -

This is the authors' abstract. We don't add key points for this paper.

The morphtropic phase boundary existing in a perovskite-type solid solution like Pb(Zr,Ti)O 3 (PZT) is reconsidered in relation to the order of the ferroelectric phase transition. For the secondorder transition from the paraelectric cubic phase, at the triple point S where the cubic, tetragonal and rhombohedral phases meet, the free energy is isotropic in the order parameter space, and a vertical boundary guarantees dielectrically excellent properties, while for the first-order transition, at the triple point F, the free energy is usually anisotropic, and even a vertical boundary does not necessarily guarantee the best properties.