Recent Understanding the Dielectric Relaxation Processes and Dipolar Disordering in High-Symmetry Relaxor System Cd₂Nb₂O₇

Abstract

Unusual polydispersive dielectric response of undiluted Cd₂Nb₂O₇ pyrochlore between 100 Hz to 6 MHz and 77 to 300 K is reported. Below T_C ≈ 198 K, the relaxation typical of (i) a normal ferroelectric (FE), (ii) a relaxor FE with glassy behaviour, and (iii) a dipolar glass develop in the system. Based on a weak bonding between the pyrochlore-structure-forming (NbO₆)ⁿ⁻ and (CdO₈)ⁿ⁻ networks, a mechanism is proposed that explains an occurrence of the orientational dipolar disorder and disordered states of different nature with decreasing temperature.

Keywords:

• Cd₂Nb₂O₇
• dielectric relaxation
• relaxors
• glasses
• pyrochlores

Acknowledgement

The financial support from KBN (Poland), Project 2P03B04722 is acknowledged.