A comprehensive study of the random dipole ferroelectrics KTN and KLT

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Abstract
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 offcenter 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.