Dielectric and Pyroelectric Properties of Cadmium Niobate Ceramics

The low‐temperature dielectric and pyroelectric properties of pyrochlore Cd₂Nb₂O₇ ceramics have been investigated over the temperature range from 10 to 300 K. Dielectric data confirmed that two ferroelectric transitions occurred in the Cd₂Nb₂O₇ ceramics at temperatures near 80 and 192 K. The higher‐temperature ferroelectric transition is complex, with evidence for three separate transitions occurring within a narrow temperature range. The temperature and frequency dependencies of the dielectric constant were consistent with both second‐order (diffuse) and improper ferroelectric (ferroelastic) effects. Pyroelectric data also confirmed the multiple‐transition behavior, with anomalies in the pyroelectric coefficient at temperatures corresponding to the onset of the diffuse ferroelectric transition and the ferroelastic effect. Dielectric loss data (analyzed by both Arrhenius and Cole‐Cole formalisms) indicated the presence of three separate relaxation‐type dielectric loss mechanisms in this temperature range. Unambiguous explanations for the observed dielectric and pyroelectric phenomena could not be made, but domain effects are believed to be responsible for at least part of the complex nature of the ferroelectric transitions in this material.