A COMPREHENSIVE STUDY OF THE RANDOM DIPOLE FERROELECTRICS KTN AND KLT

The two mixed systems KLT and KTN are characteristic of the class of the random dipole ferroelectrics. Their most salient characteristic is the random substitution of a dipolar impurity in an already strongly polarizable lattice. The dipolar character of the impurity comes from its off center position while the presence of a soft mode gives its strong polarizability to the lattice KTaO3. The combination of these two features leads, in both systems, to a very unusual phase transition and to strongly enhanced precursor effects. We give here an overview of the results obtained from a variety of experimental techniques, all to study the same set of crystals with different concentrations; (Dielectrics, Polarization, Ultrasonics, Raman and Neutron Scattering.) The cross section of all these results provides a coherent picture of the collective behavior of the two systems and of the mechanism of the transition in random dipole ferroelectrics.