Ferroelectric Properties and Electric Field Dependent Polarization in 0.86BaTiO₃–0.14(Bi_3/4Na_1/4)(Mg_1/4Ti_3/4)O₃ Ceramics

Abstract

Ceramics of composition 0.86BaTiO₃–0.14(Bi_3/4Na_1/4)(Mg_1/4Ti_3/4)O₃ (0.86BT-0.14BNMT) are synthesized and verified to be of perovskite tetragonal symmetry. The ceramics also exhibit saddle-back shaped dielectric anomalies as a function of temperature. The high temperature anomaly at T_m (∼393 K) is essentially frequency independent; the low temperature anomaly at T₁ (∼301 K at 1 kHz) however is strongly dispersive with frequency. The temperature dependence of the relaxation time, τ(T), can be fitted well with a Vogel-Fulcher type relation. The P-E relation below 228 K is of characteristic hysteresis type of a normal ferroelectric. As the temperature approaches to 333 K, the P-E loops became slim resembling relaxor characteristics. Three pyroelectric peaks were found that correspond to respective phase transitions of BaTiO₃, which indicates the dominance of ferroelectric BT clusters in the solid solution compositions.

Keywords:

• Relaxors
• lead-free materials
• dielectric properties
• local polarization

Acknowledgment

This work has been supported by the US National Science Foundation under grant number 0833000 and 0844081 and by the US Office of Naval Research under grant number N00014-08-1-0854. One of the authors (XW) acknowledges the support of National Natural Science Foundation of China (Project 50772087). LW also acknowledges the scholarship support from China Scholar Council through the program of national study-abroad project for postgraduates of high level universities.

Communicated by Dr. George W. Taylor

Notes

**Visiting scholar from Dept. of Material Physics, Xi'an Jiaotong University, Xi'an 710049, China. E-mail: [email protected]