Structure and Dielectric Properties of a New Solid Solution (1- x)PbTiO₃- x DyFeO₃

A solid solution system of novel ferroelectric (1-x)PbTiO₃-xDyFeO₃ ceramics with 0 ≤ x ≤ 0.50 has been synthesized using the solid state reaction method. The X-ray diffraction data at room temperature indicate a composition-induced structural transition from the tetragonal P4mm phase for 0 ≤ x < 0.25 to the cubic Pm-3m phase for x ≥ 0.25. Both the unit cell volume and the tetragonality gradually decrease with increasing x. The grain size of the ceramics is found by Scanning Electron Microscopy to increase first and then decrease with increasing x. The Curie point moves to low temperatures with increasing DyFeO₃ concentration and a composition-induced crossover from a normal ferroelectric phase to a ferroelectric state with diffuse phase transition has been observed. Two Havriliak-Negami relaxation processes and a significant contribution from dc conductance were found at high temperature above the temperature of dielectric maximum, T_m. The room temperature ferroelectric polarization shows a decrease with the increase of x. A partial phase diagram of the solid solution system is constructed based on the dielectric, ferroelectric and structural analyses.