Abstract: The complex dielectric response of tungsten bronze Sr_1-xBa_xNb₂O₆ [SBN(1--x)/x, x=0.40, 0.50 and 0.60] relaxor ferroelectric ceramics was
carefully studied as a function of temperature between --180℃ and 450℃. Three distinct relaxation features were observed in all the compositions.
The thermal hysteresis of dielectric maximum was considered to be associated with “lock in” of the incommensurate phase. It was confirmed by investigation of
the Curie-Weisis behavior at a higher temperature range. These results were also discussed in terms of the polarization fluctuation of polar microregions briefly.

Key words: relaxor ferroelectrics, tungsten bronze, strontium barium niobate, dielectric relaxation, incommensurate phase, polar microregion