Coexistence of ferroelectric and relaxor states in Ba2PrxNd1-xFeNb4O15

We have investigated the dielectric response of Ba
₂
Pr
_x
Nd
_1-x
FeNb
₄
O
₁₅
ceramics (x = 0, 0.2, 0.5, 0.6, 0.8, 1) in the frequency range from 20 Hz to 1 GHz. The obtained results confirmed the continuous transformation from the ferroelectric behavior of Ba
₂
NdFeNb
₄
O
₁₅
to the pure relaxor response of Ba
₂
PrFeNb
₄
O
₁₅
with increasing x. For intermediate x values, coexisting ferroelectric transition and relaxor dielectric signatures were observed, corresponding to two different phenomena in the framework of these materials. Increasing the amount of Pr decreases the ferroelectric phase transition temperatures in these ceramics; a large cooling-heating hysteresis exceeding 50K was also observed.