Structural evolution, dielectric relaxation and modulus spectroscopic studies in Dy substituted NBT-BT ferroelectric ceramics

Abstract

We report the effect of partial substitution of Dy3+ rare earth ion in NBT-BT lead free ceramics on its structural, microstructural, ferroelectric and dielectric phase transitions. The Rietveld refined X-ray diffraction analysis revealed a coexistence of dual phase with major monoclinic (Cc) along with minor tetragonal (P4mm) in all Dy-NBT-BT ceramics. The T-dependent dielectric broad band spectroscopic study revealed that Dy-substituted NBT-BT ceramics exhibits two diffuse dielectric anomalies renowned as Ferro (FE) to anti Ferro (AFE) i.e., depolarization phase transition ( $$T_{d}$$ ) and Antiferro (AFE) to paraelectric (PE) i.e., curie phase transition ( $$T_{C}$$ ), below 150 °C and well above 300 °C temperature regions respectively. The complex frequency dependent dielectric and modulus spectroscopy analysis supports the Non-Debye type dielectric relaxation process was dominated for all the measured ceramics. T-dependent AC-conductivity study revealed, thermally activated charge carries and single ionized oxygen vacancies are found to contribute conduction process at different temperature regions. Room temperature polarization hysteresis (P–E) loops analysis exposed a slim asymmetric shape with Dy substitution increasing that indicates conversion of hard to soft ferroelectric character. Remnant polarisation ( $$P_{r}$$ ) and coercive field ( $$E_{c}$$ ) decreases with dopant concentration shows the tetragonality dominance with Dy substitution. Furthermore, an optimum recoverable energy density 1.477 J/cm3 was obtained in NBT-BT at Dy = 0.03 compositions that designate the materials could be useful for future high energy storage density applications.