Fragile phase stability in (1-x)Pb(Mg1/3Nb2/3O3)-xPbTiO3 crystals: A comparisons of [001] and [110] field-cooled phase diagrams

TL;DR

This study constructs and compares phase diagrams of PMN-xPT crystals under different electric field directions, revealing fragile phase stability influenced by electric field strength and orientation, with implications for material design.

Contribution

The paper provides detailed phase diagrams for PMN-xPT crystals under [001] and [110] field-cooled conditions, highlighting the impact of electric field direction on phase stability and transitions.

Findings

Abnormal thermal expansion region above dielectric maximum extended by electric field.

Different monoclinic phases (MA, MB, MC) appear depending on field direction.

Phase boundaries between tetragonal and monoclinic phases vary with electric field orientation.

Abstract

Phase diagrams of [001] and [110] field-cooled (FC) (1-x)Pb(Mg1/3Nb2/3O3)-xPbTiO3 or PMN-xPT crystals have been constructed, based on high-resolution x-ray diffraction data. Comparisons reveal several interesting findings. First, a region of abnormal thermal expansion above the dielectric maximum was found, whose stability range extended to higher temperatures by application of electric field (E). Second, the rhombohedral (R) phase of the ZFC state was replaced by a monoclinic MA in the [001] FC diagram, but with monoclinic MB in the [110] FC. Third, the monoclinic MC phase in ZFC and [001] FC diagram was replaced by an orthorhombic (O) phase in the [110] FC. Finally, in the [001] FC diagram, the phase boundary between tetragonal (T) and MA was extended to lower PT contents (x=0.25); whereas in the [110] FC diagram, this extended region was entirely replaced by the O phase. These results clearly demonstrate that the phase stability of PMN-xPT crystals is quite fragile, depending not only on modest changes in E, but also on the direction along which that E is applied.