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

• Published in: Journal of materials science. Materials in electronics Vol. 32; no. 7; pp. 8628 - 8647
• Main Authors: Chandra Sekhar, K. S. K. R., Mahesh, M. L. V., Sreenivasu, T., Rama Krishna, Y., Chandra Mouli, K., Tirupathi, Patri
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-04-2021; Springer Nature B.V
• Subjects: Anomalies; Ceramics; Characterization and Evaluation of Materials; Chemistry and Materials Science; Coercivity; Current carriers; Depolarization; Dielectric relaxation; Dysprosium; Energy storage; Ferroelectric materials; Ferroelectricity; Flux density; Lead free; Materials Science; Metal ions; Optical and Electronic Materials; Phase transitions; Polarization; Room temperature; Spectroscopic analysis; Substitutes
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1007/s10854-021-05506-4

We report the effect of partial substitution of Dy
3+
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 (
P
4
mm
) 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/cm
3
was obtained in NBT-BT at Dy = 0.03 compositions that designate the materials could be useful for future high energy storage density applications.