Zr0.98Sn0.02TiO4 single crystal in a low electric field:: Birefringence, dielectric, and synchrotron x-ray studies

The temperature dependence of linear birefringence and complex dielectric constants of Zr0.98Sn0.02TiO4 single crystal under low de electric fields (E less than or equal to 1.5 kV/cm) have been investigated in combination with synchrotron x-ray diffraction. Two anomalies for ZrTiO4 were found to be related with the transitions to intermediate commensurate (C) phases with commensurate (or incommensurate) deviation factor delta = 1/70 and delta = 1/50 at 855 and 875 degrees C, respectively, while those of Zr0.98Sn0.02TiO4 completely vanished. This manifests that Sn impurity prevents the incommensurate (IC) phase from passing over to the intermediate C phase. A de electric (E) field made the dielectric anomaly related with IC-C phase transitions T-c split into two peaks. One in zero field has a maximum at T-c2 = 845 degrees C and its E field dependence is found to be dT(c2)/dE = 1.5 degrees C cm/kV. The other T-c1 remains nearly invariant with respect to E fields. i.e., at 845 degrees C under zero E field. It was evinced by the synchrotron x-ray diffraction not only that the E field induced phase in T-c1 < T = T-c2 consists of the C phase with delta = 0 and the IC phase with delta = 1/68, but also that the increase in E field stabilizes the C phase. The frequency (f) dependent dielectric relaxation at E = 1.0 kV/cm with 10(-5) less than or equal to f less than or equal to 10(11) Hz demonstrates three distinct dielectric modes in T-c1 < Te < T-c2. The dielectric data, just below T-c1, between T-c1 and T-c2, and just above T-c2, can be analyzed to show that the low-frequency mode is due to the pinned discommensurations, while the high-frequency one to the C phase.