Dielectric Relaxation Phenomena in SBN Single Crystals Doped with Ce

The dielectric study of $Sr_{0.73}Ba_{0.27}Nb_2O_6:Ce$ (SBN) crystals along [010] crystallographic axis was performed in the temperature region of 310-360 K and frequency range from 25 Hz up to 1 MHz. The thermal dipole relaxation of quasi-Debye-type for this orientation of sample was observed in both investigated structural phases. The phase transition was most clearly seen from the temperature dependence of the relaxation time at $T_{c}$ = 320 K. The relaxation processes were related to the collective oscillations of the Nb-O bonds in the two different type corner-sharing $NbO_6$ octahedra aligned along c-axis.