Abstract

The microwave dielectric loss of stoichiometric and non-stoichiometric Ba(Co1/3Nb2/3)O3 ceramics have been measured from 2 to 300 K in magnetic fields ranging from 0 to 5 T using a dielectric resonator (DR) technique. The microwave absorption from spin excitations of unpaired d-electrons in exchange coupled Co2+ ions dominate the loss of the Ba(Co1/3Nb2/3)O3 ceramics at cryogenic temperatures. Two peaks in the loss tangent (tan δ) vs temperature relation from a distinctly different origin occur at 25-30 K and 90 K, which increase in magnitude with increasing Co content in the bulk dielectric samples. Evidence that these peaks result from polaron conduction from hopping between Co2+ and Co3+ ions includes (i) the peak's observed temperature range; (ii) the decrease in peak intensity of approximately a factor of two in a large applied magnetic fields (5 T); and (iii) a strong correlation between the peak's magnitude and both the fraction of the minority Co3+ in the dominant Co2+ matrix and D.C. conductivity at elevated temperatures. A magnetic-field independent high temperature peak with a maximum at 250 K dominates the room temperature microwave loss whose magnitude correlates with those of the low temperature peaks. This suggests that the defects responsible for carrier conduction play an important role in establishing the loss tangent at room temperature.

Original languageEnglish (US)
JournalJournal of the American Ceramic Society
DOIs
StateAccepted/In press - Jan 1 2017

Fingerprint

Dielectric losses
ceramics
Microwaves
temperature
magnetic field
Temperature
Magnetic fields
ion
Ions
Gene Conversion
Dielectric resonators
defect
loss
microwave
conductivity
Cryogenics
electron
Ion exchange
matrix
Defects

Keywords

  • Complex perovskite
  • Dielectric loss
  • Dipole relaxation
  • Microwave resonator
  • Point defect

ASJC Scopus subject areas

  • Ceramics and Composites
  • Geology
  • Geochemistry and Petrology
  • Materials Chemistry

Cite this

Sayyadi-Shahraki, A., Taheri-Nassaj, E., Sharifi, H., Gonzales, J., Kolodiazhnyi, T., & Newman, N. (Accepted/In press). Origin of dielectric loss in Ba(Co1/3Nb2/3)O3 microwave ceramics. Journal of the American Ceramic Society. https://doi.org/10.1111/jace.15343

Origin of dielectric loss in Ba(Co1/3Nb2/3)O3 microwave ceramics. / Sayyadi-Shahraki, Ahmad; Taheri-Nassaj, Ehsan; Sharifi, Hassan; Gonzales, Justin; Kolodiazhnyi, Taras; Newman, Nathan.

In: Journal of the American Ceramic Society, 01.01.2017.

Research output: Contribution to journalArticle

Sayyadi-Shahraki, Ahmad ; Taheri-Nassaj, Ehsan ; Sharifi, Hassan ; Gonzales, Justin ; Kolodiazhnyi, Taras ; Newman, Nathan. / Origin of dielectric loss in Ba(Co1/3Nb2/3)O3 microwave ceramics. In: Journal of the American Ceramic Society. 2017.
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