Structural and Dielectric Studies of the Phase Transitions in Pb(Yb1/2Ta1/2)O3-PbTiO3 Ceramics

A dielectric phase diagram of the pseudobinary (1-x)Pb(Yb1/2Ta1/2)O3-xPbTiO3 solid solution system was determined. The crystal structures and the dielectric properties were investigated in terms of the PbTiO3 concentration. As the PbTiO3 concentration increases, the crystal structure changes from monoclinic to pseudocubic and then to tetragonal. A morphotropic phase boundary that separates the pseudocubic phase from the tetragonal phase has been determined at x ≈0.5. The phase transition of pure Pb(Yb1/2Ta1/2)O3 is unusual in that it undergoes a paraelectric-antiferroelectric transition at 310°C and another secondary antiferroelectric-ferroelectric transition at about 177°C. This successive phase transition characteristic confers a rather unique feature on the (1-x)Pb(Yb1/2Ta1/2)O3-xPbTiO3 phase diagram.