Abstract

Phase diagrams of [001] and [110] field-cooled (FC) (1-x)Pb(Mg1/3Nb2/3O3)-xPbTiO3 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≠a) 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.

 

Biography

Hu Cao is a Ph. D. candidate at MSE of Virginia Tech. He obtained the MS degree at Shanghai Institute of Ceramics, Chinese Academy of Science on July, 2002. His thesis emphasizes on the relationship between properties and structure of relaxor ferroelectric (1- x )Pb(Mg 1/3 Nb 2/3 O 3 )- x PbTiO 3 crystals and magnetostricve Fe-xGa alloy.