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Origin of dielectric loss in Ba(Co 1/3 Nb 2/3 )O 3 microwave ceramics
Author(s) -
SayyadiShahraki Ahmad,
TaheriNassaj Ehsan,
Sharifi Hassan,
Gonzales Justin,
Kolodiazhnyi Taras,
Newman Nathan
Publication year - 2018
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.15343
Subject(s) - dielectric loss , analytical chemistry (journal) , polaron , materials science , dissipation factor , dielectric , microwave , condensed matter physics , atmospheric temperature range , conductivity , electrical resistivity and conductivity , ion , nuclear magnetic resonance , electron , chemistry , thermodynamics , physics , optoelectronics , organic chemistry , chromatography , quantum mechanics
The microwave dielectric loss of stoichiometric and non‐stoichiometric Ba(Co 1/3 Nb 2/3 )O 3 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 Co 2+ ions dominate the loss of the Ba(Co 1/3 Nb 2/3 )O 3 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 Co 2+ and Co 3+ 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 Co 3+ in the dominant Co 2+ 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.