Dielectric relaxation in Bi₂Ti₂O₇ single crystals

Abstract

Large impurity-free Bi₂Ti₂O₇ single crystals were grown by slow cooling of a melt. Their crystal structure and dielectric properties as a function of temperature at different frequencies were studied for the first time. A step-like frequency-dependent anomaly was observed at a temperature of about 220 K at a frequency of 1 kHz. The relaxation behavior is well described by the empirical Vogel-Fulcher relation typical for relaxor ferroelectrics. Based on the value of fitting parameters, Bi₂Ti₂O₇ occupies an intermediate position between the canonical relaxor PbMg_1/3Nb_2/3O₃ on the one hand and lead-free relaxors based on BaTiO₃ on the other hand. The possible mechanisms of the observed dielectric relaxation of the Bi₂Ti₂O₇ single crystals are discussed.

Keywords:

• Pyrochlore
• dielectric properties
• relaxor ferroelectrics
• bismuth titanate
• single crystal