Defect dipole induced improved electrocaloric effect in modified NBT-6BT lead-free ceramics

Koyal Suman Samantaray; Ruhul Amin; E. G. Rini; Indranil Bhaumik; A. Mekki; K. Harrabi; Somaditya Sen

doi:10.1016/j.jallcom.2022.163837

Defect dipole induced improved electrocaloric effect in modified NBT-6BT lead-free ceramics

Koyal Suman Samantaray, Ruhul Amin, E. G. Rini, Indranil Bhaumik, A. Mekki, K. Harrabi, Somaditya Sen^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

3 Scopus citations

Abstract

The Rietveld refinement of the polycrystalline powders of 1% Fe and Mn-doped (Na_0.5Bi_0.5)_0.94Ba_0.06Ti_0.98V_0.02O₃ at the Ti-site confirmed a single rhombohedral (R3c) phase. The bandgap, (E_g) was affected by the anti-phase octahedral tilt angle and the spin-orbit splitting energy of Ti⁴⁺2p_3/2 and Ti⁴⁺2p_1/2 states. The decrease in Bi loss and increase in the binding energy of Ba due to Fe/Mn doping has been correlated to the strengthening of Bi-O and Ba-O bonds which was revealed from the XPS studies thereby further related to the average A-O bond length from structural studies. Hence, a reduction of oxygen vacancy (V_O) for the doped samples has been justified. A significant improvement of the dielectric constant, relaxation time (τ₀), and the decrease in conductivity due to doping was revealed from the frequency-dependent (10 Hz-1 MHz) dielectric measurement study. The conduction and relaxation process are dominated by the short-range movement of defects. The activation energy (E_a ~1 eV) revealed that there is a presence of double-ionized V_Os. The ECE study showed a significant enhancement of the changes in entropy, ΔS, and the adiabatic temperature difference, ΔT, due to doping, with ΔT being highest in the Fe-doped sample. Such improvement of dielectric and ECE properties was confirmed due to the reduction of the mobility of oxygen vacancy because of the formation(Mn_Ti^′′−V_o^••)/(Mn_Ti^′−V_o^••)^• and Fe_Ti^′′−V_o^••/(Fe_Ti^′−V_o^••)^• defect dipoles.

Original language	English
Article number	163837
Journal	Journal of Alloys and Compounds
Volume	903
DOIs	https://doi.org/10.1016/j.jallcom.2022.163837
State	Published - 15 May 2022

Bibliographical note

Funding Information:
The authors would like to acknowledge the facilities at IIT Indore. A. Mekki, K. Harrabi, and S. Sen gratefully acknowledge the support of the King Fahd University of Petroleum and Minerals, Saudi Arabia, under the DF191055 DSR project. Ms. Koyal Suman Samantaray acknowledges MHRD for providing Prime Minister Research Fellowship (PMRF). Mr. Ruhul Amin acknowledges DST for INSPIRE Fellowship (No. IF160339). E.G Rini also acknowledges the DST, India for financial support under Women Scientist Scheme (SR/WOS-A/PM-99/2016 (G)).

Funding Information:
The authors would like to acknowledge the facilities at IIT Indore. A. Mekki, K. Harrabi, and S. Sen gratefully acknowledge the support of the King Fahd University of Petroleum and Minerals , Saudi Arabia, under the DF191055 DSR project. Ms. Koyal Suman Samantaray acknowledges MHRD for providing Prime Minister Research Fellowship (PMRF). Mr. Ruhul Amin acknowledges DST for INSPIRE Fellowship (No. IF160339 ). E.G Rini also acknowledges the DST, India for financial support under Women Scientist Scheme (SR/WOS-A/PM-99/2016 (G)).

Publisher Copyright:
© 2022 Elsevier B.V.

Keywords

Defect dipoles
Dielectric
Electrocaloric effect
Ferroelectric
Lead-free perovskites

ASJC Scopus subject areas

Mechanics of Materials
Mechanical Engineering
Metals and Alloys
Materials Chemistry

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10.1016/j.jallcom.2022.163837

Cite this

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title = "Defect dipole induced improved electrocaloric effect in modified NBT-6BT lead-free ceramics",

abstract = "The Rietveld refinement of the polycrystalline powders of 1% Fe and Mn-doped (Na0.5Bi0.5)0.94Ba0.06Ti0.98V0.02O3 at the Ti-site confirmed a single rhombohedral (R3c) phase. The bandgap, (Eg) was affected by the anti-phase octahedral tilt angle and the spin-orbit splitting energy of Ti4+2p3/2 and Ti4+2p1/2 states. The decrease in Bi loss and increase in the binding energy of Ba due to Fe/Mn doping has been correlated to the strengthening of Bi-O and Ba-O bonds which was revealed from the XPS studies thereby further related to the average A-O bond length from structural studies. Hence, a reduction of oxygen vacancy (VO) for the doped samples has been justified. A significant improvement of the dielectric constant, relaxation time (τ0), and the decrease in conductivity due to doping was revealed from the frequency-dependent (10 Hz-1 MHz) dielectric measurement study. The conduction and relaxation process are dominated by the short-range movement of defects. The activation energy (Ea ~1 eV) revealed that there is a presence of double-ionized VOs. The ECE study showed a significant enhancement of the changes in entropy, ΔS, and the adiabatic temperature difference, ΔT, due to doping, with ΔT being highest in the Fe-doped sample. Such improvement of dielectric and ECE properties was confirmed due to the reduction of the mobility of oxygen vacancy because of the formation(MnTi′′−Vo••)/(MnTi′−Vo••)• and FeTi′′−Vo••/(FeTi′−Vo••)• defect dipoles.",

keywords = "Defect dipoles, Dielectric, Electrocaloric effect, Ferroelectric, Lead-free perovskites",

author = "Samantaray, {Koyal Suman} and Ruhul Amin and Rini, {E. G.} and Indranil Bhaumik and A. Mekki and K. Harrabi and Somaditya Sen",

note = "Funding Information: The authors would like to acknowledge the facilities at IIT Indore. A. Mekki, K. Harrabi, and S. Sen gratefully acknowledge the support of the King Fahd University of Petroleum and Minerals, Saudi Arabia, under the DF191055 DSR project. Ms. Koyal Suman Samantaray acknowledges MHRD for providing Prime Minister Research Fellowship (PMRF). Mr. Ruhul Amin acknowledges DST for INSPIRE Fellowship (No. IF160339). E.G Rini also acknowledges the DST, India for financial support under Women Scientist Scheme (SR/WOS-A/PM-99/2016 (G)). Funding Information: The authors would like to acknowledge the facilities at IIT Indore. A. Mekki, K. Harrabi, and S. Sen gratefully acknowledge the support of the King Fahd University of Petroleum and Minerals , Saudi Arabia, under the DF191055 DSR project. Ms. Koyal Suman Samantaray acknowledges MHRD for providing Prime Minister Research Fellowship (PMRF). Mr. Ruhul Amin acknowledges DST for INSPIRE Fellowship (No. IF160339 ). E.G Rini also acknowledges the DST, India for financial support under Women Scientist Scheme (SR/WOS-A/PM-99/2016 (G)). Publisher Copyright: {\textcopyright} 2022 Elsevier B.V.",

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day = "15",

doi = "10.1016/j.jallcom.2022.163837",

language = "English",

volume = "903",

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T1 - Defect dipole induced improved electrocaloric effect in modified NBT-6BT lead-free ceramics

AU - Samantaray, Koyal Suman

AU - Amin, Ruhul

AU - Rini, E. G.

AU - Bhaumik, Indranil

AU - Mekki, A.

AU - Harrabi, K.

AU - Sen, Somaditya

N1 - Funding Information: The authors would like to acknowledge the facilities at IIT Indore. A. Mekki, K. Harrabi, and S. Sen gratefully acknowledge the support of the King Fahd University of Petroleum and Minerals, Saudi Arabia, under the DF191055 DSR project. Ms. Koyal Suman Samantaray acknowledges MHRD for providing Prime Minister Research Fellowship (PMRF). Mr. Ruhul Amin acknowledges DST for INSPIRE Fellowship (No. IF160339). E.G Rini also acknowledges the DST, India for financial support under Women Scientist Scheme (SR/WOS-A/PM-99/2016 (G)). Funding Information: The authors would like to acknowledge the facilities at IIT Indore. A. Mekki, K. Harrabi, and S. Sen gratefully acknowledge the support of the King Fahd University of Petroleum and Minerals , Saudi Arabia, under the DF191055 DSR project. Ms. Koyal Suman Samantaray acknowledges MHRD for providing Prime Minister Research Fellowship (PMRF). Mr. Ruhul Amin acknowledges DST for INSPIRE Fellowship (No. IF160339 ). E.G Rini also acknowledges the DST, India for financial support under Women Scientist Scheme (SR/WOS-A/PM-99/2016 (G)). Publisher Copyright: © 2022 Elsevier B.V.

PY - 2022/5/15

Y1 - 2022/5/15

N2 - The Rietveld refinement of the polycrystalline powders of 1% Fe and Mn-doped (Na0.5Bi0.5)0.94Ba0.06Ti0.98V0.02O3 at the Ti-site confirmed a single rhombohedral (R3c) phase. The bandgap, (Eg) was affected by the anti-phase octahedral tilt angle and the spin-orbit splitting energy of Ti4+2p3/2 and Ti4+2p1/2 states. The decrease in Bi loss and increase in the binding energy of Ba due to Fe/Mn doping has been correlated to the strengthening of Bi-O and Ba-O bonds which was revealed from the XPS studies thereby further related to the average A-O bond length from structural studies. Hence, a reduction of oxygen vacancy (VO) for the doped samples has been justified. A significant improvement of the dielectric constant, relaxation time (τ0), and the decrease in conductivity due to doping was revealed from the frequency-dependent (10 Hz-1 MHz) dielectric measurement study. The conduction and relaxation process are dominated by the short-range movement of defects. The activation energy (Ea ~1 eV) revealed that there is a presence of double-ionized VOs. The ECE study showed a significant enhancement of the changes in entropy, ΔS, and the adiabatic temperature difference, ΔT, due to doping, with ΔT being highest in the Fe-doped sample. Such improvement of dielectric and ECE properties was confirmed due to the reduction of the mobility of oxygen vacancy because of the formation(MnTi′′−Vo••)/(MnTi′−Vo••)• and FeTi′′−Vo••/(FeTi′−Vo••)• defect dipoles.

AB - The Rietveld refinement of the polycrystalline powders of 1% Fe and Mn-doped (Na0.5Bi0.5)0.94Ba0.06Ti0.98V0.02O3 at the Ti-site confirmed a single rhombohedral (R3c) phase. The bandgap, (Eg) was affected by the anti-phase octahedral tilt angle and the spin-orbit splitting energy of Ti4+2p3/2 and Ti4+2p1/2 states. The decrease in Bi loss and increase in the binding energy of Ba due to Fe/Mn doping has been correlated to the strengthening of Bi-O and Ba-O bonds which was revealed from the XPS studies thereby further related to the average A-O bond length from structural studies. Hence, a reduction of oxygen vacancy (VO) for the doped samples has been justified. A significant improvement of the dielectric constant, relaxation time (τ0), and the decrease in conductivity due to doping was revealed from the frequency-dependent (10 Hz-1 MHz) dielectric measurement study. The conduction and relaxation process are dominated by the short-range movement of defects. The activation energy (Ea ~1 eV) revealed that there is a presence of double-ionized VOs. The ECE study showed a significant enhancement of the changes in entropy, ΔS, and the adiabatic temperature difference, ΔT, due to doping, with ΔT being highest in the Fe-doped sample. Such improvement of dielectric and ECE properties was confirmed due to the reduction of the mobility of oxygen vacancy because of the formation(MnTi′′−Vo••)/(MnTi′−Vo••)• and FeTi′′−Vo••/(FeTi′−Vo••)• defect dipoles.

KW - Defect dipoles

KW - Dielectric

KW - Electrocaloric effect

KW - Ferroelectric

KW - Lead-free perovskites

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DO - 10.1016/j.jallcom.2022.163837

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JO - Journal of Alloys and Compounds

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ER -

Defect dipole induced improved electrocaloric effect in modified NBT-6BT lead-free ceramics

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

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