Effect of Ba substitution on structural, electrical and thermal properties of La0.65Ca0.35 - xBaxMnO3(0 ≤ x ≤ 0.25) manganites

S. O. Manjunatha, Ashok Rao, T. Y. Lin, C. M. Chang, Y. K. Kuo

Research output: Contribution to journalArticle

37 Citations (Scopus)

Abstract

In the present communication, the effect of Ba substitution on the structural, mechanical, electrical transport and thermal properties of La0.65Ca0.35 - xBaxMnO3(0.00 ≤ x ≤ 0.25) manganites have been investigated. Rietveld refinement of XRD data reveals that all samples are single phase. With increasing Ba content, a transformation of crystal structure from rhombohedral (x = 0.00-0.15) to cubic symmetry (x = 0.25) is observed. In the micro-hardness study, a correlation between the average grain size and micro-hardness is concluded. It is found that all samples exhibit a clear metal-insulator transition, and the transition temperature (TMI) shifts monotonically towards higher temperature. The Seebeck coefficient (S) of the pristine sample is negative in the entire temperature range, whereas for all doped samples the measured S exhibits a crossover from positive to negative values. The analysis of Seebeck coefficient data indicates that the small polaron hopping model is operative in the high temperature region. The room-temperature magnitude of thermal conductivity, κ of the studied samples is in the range of 20-35 mW/cm K and such low value is presumably attributed to the Jahn Teller (J-T) effect. An analysis of κ using Wiedemann-Franz's (W-F) law confirms that the total thermal conductivity is mainly associated with the lattice phonons rather than charge carriers. The change in entropy associated with the transition evaluated from the specific heat measurements is found to decrease with increasing x, most likely due to the enhancement of magnetic inhomogeneity in these manganites.

Original languageEnglish
Pages (from-to)303-310
Number of pages8
JournalJournal of Alloys and Compounds
Volume619
DOIs
Publication statusPublished - 15-01-2015

Fingerprint

Manganites
Structural properties
Electric properties
Substitution reactions
Thermodynamic properties
Seebeck coefficient
Microhardness
Thermal conductivity
Thermal variables measurement
Jahn-Teller effect
Gene Conversion
Temperature
Rietveld refinement
Metal insulator transition
Phonons
Charge carriers
Crystal lattices
Transport properties
Superconducting transition temperature
Specific heat

All Science Journal Classification (ASJC) codes

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

Cite this

@article{bf81697dfc8a4fd781fe05ef29244f08,
title = "Effect of Ba substitution on structural, electrical and thermal properties of La0.65Ca0.35 - xBaxMnO3(0 ≤ x ≤ 0.25) manganites",
abstract = "In the present communication, the effect of Ba substitution on the structural, mechanical, electrical transport and thermal properties of La0.65Ca0.35 - xBaxMnO3(0.00 ≤ x ≤ 0.25) manganites have been investigated. Rietveld refinement of XRD data reveals that all samples are single phase. With increasing Ba content, a transformation of crystal structure from rhombohedral (x = 0.00-0.15) to cubic symmetry (x = 0.25) is observed. In the micro-hardness study, a correlation between the average grain size and micro-hardness is concluded. It is found that all samples exhibit a clear metal-insulator transition, and the transition temperature (TMI) shifts monotonically towards higher temperature. The Seebeck coefficient (S) of the pristine sample is negative in the entire temperature range, whereas for all doped samples the measured S exhibits a crossover from positive to negative values. The analysis of Seebeck coefficient data indicates that the small polaron hopping model is operative in the high temperature region. The room-temperature magnitude of thermal conductivity, κ of the studied samples is in the range of 20-35 mW/cm K and such low value is presumably attributed to the Jahn Teller (J-T) effect. An analysis of κ using Wiedemann-Franz's (W-F) law confirms that the total thermal conductivity is mainly associated with the lattice phonons rather than charge carriers. The change in entropy associated with the transition evaluated from the specific heat measurements is found to decrease with increasing x, most likely due to the enhancement of magnetic inhomogeneity in these manganites.",
author = "Manjunatha, {S. O.} and Ashok Rao and Lin, {T. Y.} and Chang, {C. M.} and Kuo, {Y. K.}",
year = "2015",
month = "1",
day = "15",
doi = "10.1016/j.jallcom.2014.09.042",
language = "English",
volume = "619",
pages = "303--310",
journal = "Journal of Alloys and Compounds",
issn = "0925-8388",
publisher = "Elsevier BV",

}

Effect of Ba substitution on structural, electrical and thermal properties of La0.65Ca0.35 - xBaxMnO3(0 ≤ x ≤ 0.25) manganites. / Manjunatha, S. O.; Rao, Ashok; Lin, T. Y.; Chang, C. M.; Kuo, Y. K.

In: Journal of Alloys and Compounds, Vol. 619, 15.01.2015, p. 303-310.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Effect of Ba substitution on structural, electrical and thermal properties of La0.65Ca0.35 - xBaxMnO3(0 ≤ x ≤ 0.25) manganites

AU - Manjunatha, S. O.

AU - Rao, Ashok

AU - Lin, T. Y.

AU - Chang, C. M.

AU - Kuo, Y. K.

PY - 2015/1/15

Y1 - 2015/1/15

N2 - In the present communication, the effect of Ba substitution on the structural, mechanical, electrical transport and thermal properties of La0.65Ca0.35 - xBaxMnO3(0.00 ≤ x ≤ 0.25) manganites have been investigated. Rietveld refinement of XRD data reveals that all samples are single phase. With increasing Ba content, a transformation of crystal structure from rhombohedral (x = 0.00-0.15) to cubic symmetry (x = 0.25) is observed. In the micro-hardness study, a correlation between the average grain size and micro-hardness is concluded. It is found that all samples exhibit a clear metal-insulator transition, and the transition temperature (TMI) shifts monotonically towards higher temperature. The Seebeck coefficient (S) of the pristine sample is negative in the entire temperature range, whereas for all doped samples the measured S exhibits a crossover from positive to negative values. The analysis of Seebeck coefficient data indicates that the small polaron hopping model is operative in the high temperature region. The room-temperature magnitude of thermal conductivity, κ of the studied samples is in the range of 20-35 mW/cm K and such low value is presumably attributed to the Jahn Teller (J-T) effect. An analysis of κ using Wiedemann-Franz's (W-F) law confirms that the total thermal conductivity is mainly associated with the lattice phonons rather than charge carriers. The change in entropy associated with the transition evaluated from the specific heat measurements is found to decrease with increasing x, most likely due to the enhancement of magnetic inhomogeneity in these manganites.

AB - In the present communication, the effect of Ba substitution on the structural, mechanical, electrical transport and thermal properties of La0.65Ca0.35 - xBaxMnO3(0.00 ≤ x ≤ 0.25) manganites have been investigated. Rietveld refinement of XRD data reveals that all samples are single phase. With increasing Ba content, a transformation of crystal structure from rhombohedral (x = 0.00-0.15) to cubic symmetry (x = 0.25) is observed. In the micro-hardness study, a correlation between the average grain size and micro-hardness is concluded. It is found that all samples exhibit a clear metal-insulator transition, and the transition temperature (TMI) shifts monotonically towards higher temperature. The Seebeck coefficient (S) of the pristine sample is negative in the entire temperature range, whereas for all doped samples the measured S exhibits a crossover from positive to negative values. The analysis of Seebeck coefficient data indicates that the small polaron hopping model is operative in the high temperature region. The room-temperature magnitude of thermal conductivity, κ of the studied samples is in the range of 20-35 mW/cm K and such low value is presumably attributed to the Jahn Teller (J-T) effect. An analysis of κ using Wiedemann-Franz's (W-F) law confirms that the total thermal conductivity is mainly associated with the lattice phonons rather than charge carriers. The change in entropy associated with the transition evaluated from the specific heat measurements is found to decrease with increasing x, most likely due to the enhancement of magnetic inhomogeneity in these manganites.

UR - http://www.scopus.com/inward/record.url?scp=84907572359&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84907572359&partnerID=8YFLogxK

U2 - 10.1016/j.jallcom.2014.09.042

DO - 10.1016/j.jallcom.2014.09.042

M3 - Article

VL - 619

SP - 303

EP - 310

JO - Journal of Alloys and Compounds

JF - Journal of Alloys and Compounds

SN - 0925-8388

ER -