Dielectric properties and lattice dynamics of Ca-doped KLiTaO

Wakimoto, Shuichi  ; Samara, G. A.*; Grubbs, R. K.*; Venturini, E. L.*; Boatner, L. A.*; Xu, G. Y.*; Shirane, Gen*; Lee, S.-H.*

Relaxor behavior and lattice dynamics have been studied for a single crystal of KLiTaO , where a small amount of a Ca impurity ( ppm) is incorporated. The dielectric measurements revealed Debye-like relaxations of Li dipoles and the Li-Li dipolar pairs below 200K. In the neutron scattering, diffuse scattering appears around the nuclear Bragg peaks below K and phonon line broadening features start to appear at even higher temperatures suggesting that polar nano-regions (PNR's) start to form at these temperatures accomapied with the relaxational behavior of Li ions. From analyses of the diffuse intensities, the displacements include a uniform phase shift of all of the atoms in addition to the atomic displacements corresponding to a polarization vector of the transverse optic soft ferroelectric mode, a finding that is analogous to that in the prototypical relaxor material PMN.