Time evolution of polar regions in (Sr_0.65Ba_0.35)₂NaNb₅O₁₅ single crystal

Abstract

The linear, second-order and third-order dielectric susceptibilities χ₁, χ₂, χ₃ of a (Sr_0.65Ba_0.35)₂NaNb₅O₁₅ (SBNN) single crystal have been measured. Strong relaxation was found in all investigated dielectric susceptibilities near the phase transition. The time dependence of linear and third-order dielectric susceptibility can be explained as the effect of polar nano-clusters evolution. Near the phase transition, the net polarization of the crystal, monitored by second-order dielectric susceptibility, changes both its value and orientation. Measurements of the pyroelectric effect indicate that the non-zero net polarization in SBNN crystals appears spontaneously. In addition, the ferroelectric phase transition in SBNN showed many features of a first-order phase transition.

Keywords:

• Relaxor
• Phase transition
• Linear and nonlinear dielectric susceptibilities
• Aging
• Polar nano-regions

Acknowledgements

Financial support by KBN under grant 4 T08A 007 25 and partial support from the Harbin Institute of Technology to W. Cao are gratefully acknowledged.