EPR evidence for activation of trap centers in PTCR BaTiO/sub 3/ ceramics
Journal Article
·
· Mater. Res. Bull.; (United States)
Donor-doped BaTiO/sub 3/ ceramics, exhibiting PTCR, showed an EPR signal with g=1.997 which acquires high intensity above T /SUB C/ . This is indicative of activation of the corresponding defect centers, possibly V' /SUB Ba./ . The intensity of g=1.997 varies with Ba/Ti ratio, rate of cooling from the sintering temperature and the addition of TiO/sub 2/ as sintering agent. The signal intensity decreases with increase in grain size and is weak in La-doped BaTiO/sub 3/ single crystals. Therefore the concentration of V /SUB Ba/ is more around the grain boundaries than that in the bulk of grains. Activated trap centers around T /SUB C/ also arises from background impurities; those with change of electronic state: M /SUP n+1/ +e' = M /SUP n+/ (eg:-Mn) and those associated with oxygen vacancies: M /SUP p+/ -V /SUB O/ (e') (eg:-Fe/sup 3 +/). Activation of these trap centers are not dependent on the disappearance of spontaneous polarization but to the structural changes during phase transformation. The trapped charge carriers are not available for conduction and hence the increase in electrical resistivity.
- Research Organization:
- Materials Research Laboratory, Indian Institute of Science, Bangalore
- OSTI ID:
- 5036692
- Journal Information:
- Mater. Res. Bull.; (United States), Journal Name: Mater. Res. Bull.; (United States) Vol. 20:5; ISSN MRBUA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
ACTIVATION ENERGY
ADDITIVES
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM OXIDES
CERAMICS
CHALCOGENIDES
CHEMICAL COMPOSITION
CRITICAL TEMPERATURE
ELECTRON SPIN RESONANCE
ENERGY
FABRICATION
IMPURITIES
MAGNETIC RESONANCE
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RESONANCE
SINTERING
THERMODYNAMIC PROPERTIES
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE
TRAPS
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
ACTIVATION ENERGY
ADDITIVES
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM OXIDES
CERAMICS
CHALCOGENIDES
CHEMICAL COMPOSITION
CRITICAL TEMPERATURE
ELECTRON SPIN RESONANCE
ENERGY
FABRICATION
IMPURITIES
MAGNETIC RESONANCE
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RESONANCE
SINTERING
THERMODYNAMIC PROPERTIES
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE
TRAPS