Grain Boundary Oxidation in PTCR Barium Titanate Thermistors

The phenomenon of grain boundary oxidation in PTCR BaTiO3 thermistors is discussed. In particular, the energy spectra of the surface states were calculated for different samples, and these were related to the nominal composition, the impurity content of the base BaTiO3 powder used, and the prevalent...

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Bibliographic Details
Published in:Journal of the American Ceramic Society 1993-02, Vol.76 (2), p.401-408
Main Authors: Alles, Aldo B., Burdick, Vernon L.
Format: Article
Language:English
Subjects:
360205 - Ceramics, Cermets, & Refractories- Corrosion & Erosion
ALKALINE EARTH METAL COMPOUNDS
ANNEALING
Applied sciences
BARIUM COMPOUNDS
Building materials. Ceramics. Glasses
CATIONS
Ceramic industries
CERAMICS
CHARGED PARTICLES
Chemical industry and chemicals
CHEMICAL REACTIONS
CHEMISORPTION
COOLING
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
Electrotechnical and electronic ceramics
ELEMENTS
ENERGY SPECTRA
Exact sciences and technology
GRAIN BOUNDARIES
HEAT TREATMENTS
IONS
MANGANESE
MATERIALS
MATERIALS SCIENCE
METALS
MICROSTRUCTURE
N-TYPE CONDUCTORS
OXIDATION
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
POWDERS
SCHOTTKY BARRIER DIODES
SEMICONDUCTOR DEVICES
SEMICONDUCTOR DIODES
SEMICONDUCTOR MATERIALS
SEPARATION PROCESSES
SORPTION
SPECTRA
Technical ceramics
THERMISTORS
TITANATES
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
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Summary:The phenomenon of grain boundary oxidation in PTCR BaTiO3 thermistors is discussed. In particular, the energy spectra of the surface states were calculated for different samples, and these were related to the nominal composition, the impurity content of the base BaTiO3 powder used, and the prevalent atmospheric conditions during cooling and/or annealing. It is proposed that the interaction of manganese with oxygen creates deep‐lying traps, and, in general, some proof is offered that the majority of the surface states are due to different oxidizing chemisorbed gases. It is believed that the ability of a particular sample to adsorb such gases in adequate amounts, and thus exhibit an appreciable PTCR effect, is related to the presence of acceptor‐type dopants perferentially segregated onto the grain surfaces. Notably, the role of 3d transition metal cations in this process is discussed in some detail.
ISSN:0002-7820
1551-2916
DOI:10.1111/j.1151-2916.1993.tb03798.x