Structural study of Pb(Fe2/3W1/3)O-3-PbTiO3 system

The crystalline structure of the solid solution (1-x)Pb(Fe2/3W1/3)O3-xPbTiO3 (PFW-PT) with x=0, 0.2, 0.25, 0.3, 0.35, 0.4 and 1 was analysed using X-ray diffraction (XRD) with comparative cell-refinement methods, in order to detect the change in symmetry with composition. Pure PFW shows pseudo-cubic symmetry for temperatures in the range 85-423 K. For the temperatures T=85 K and T=300 K, the solid solutions have cubic or tetragonal structures. The cell constants are functions of PbTiO3 amount. A temperature-dependent Morphotropic Phase Boundary (MPB) separating the pseudo-cubic (relaxor) and tetragonal (ferroelectric) phases might be present. The ranges of compositions for this boundary are: x<0.2 at T=85 K and x?(0.3,0.35) for T=300 K.