Structural and dielectric studies of the phase transitions in Pb(Yb1/2Ta1/2)O-3-PbTiO3 ceramics

A dielectric phase diagram of the pseudobinary (1 - x)Pb(Yb1/2Ta1/2)O-3-xPb TiO(3) solid solution system was determined: The crystal structures and the dielectric properties were investigated in terms of the PbTiO3 concentrati on. As the PbTiO3 concentration increases, the crystal structure changes fr om monoclinic to pseudocubic and then to tetragonal. A morphotropic phase b oundary that separates the pseudocubic phase from the tetragonal phase has been determined at x approximate to 0.5. The phase transition of pure Pb(Yb 1/2Ta1/2)O-3 is unusual in that it undergoes a paraelectric-antiferroelecrr ic transition at 310 degreesC and another secondary antiferroelectric-ferro electric transition at about 177 degreesC. This successive phase transition characteristic confers a rather unique feature on the (1 - X)Pb(Yb1/2Ta1/2 )O-3-xPbTiO(3) phase diagram.