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Fragile phase stability in (1-x)Pb(Mg1/3Nb2/3O3)-xPbTiO(3) crystals: A comparison of 001 and 110 field-cooled phase diagrams
Viehland, Dwight D.
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Phase diagrams of  and  field-cooled (FC) (1-x)Pb(Mg1/3Nb2/3O3)-xPbTiO(3) or PMN-xPT (0.15 <= x <= 0.38) crystals have been constructed, based on high-resolution x-ray diffraction data. Comparisons reveal several interesting findings. First, a region of abnormal thermal expansion (c not equal a) above the dielectric maximum was found, whose stability range extended to higher temperatures on application of electric field (E). Second, the rhombohedral (R) phase of the zero-field-cooled (ZFC) state was replaced by monoclinic M-A in the  FC diagram, but with monoclinic M-B in the  FC. Third, the monoclinic M-C phase in the ZFC and  FC diagram was replaced by an orthorhombic (O) phase in the  FC diagram. Finally, in the  FC diagram, the phase boundary between tetragonal (T) and M-A phases was extended to lower PT content (x=0.25); whereas in the  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 E is applied.