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Depletion‐layer Dielectric Properties of Positive Temperature Coefficient of Resistance Barium Titanate
Author(s) -
Wang Da Yu,
Umeya Kazumasa
Publication year - 1990
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/j.1151-2916.1990.tb09798.x
Subject(s) - barium titanate , materials science , curie temperature , grain boundary , temperature coefficient , dielectric , condensed matter physics , phase boundary , impurity , transition point , mineralogy , ceramic , composite material , thermodynamics , phase (matter) , microstructure , chemistry , physics , optoelectronics , organic chemistry , ferromagnetism
For pure and impurity‐added positive temperature coefficient of resistance (PTCR) barium titanate ceramic samples, a −11°C shift of the Curie point at the grain‐boundary/depletion‐layer region was observed. This result is obtained by fitting the PTCR grain‐boundary resistance and capacitance data to a theory which combines a double‐depletion‐layer model with the Devonshire thermodynamic theory of barium titanate. The parameters used in the fitting are obtained from independent experiments. The shift of the Curie point is believed to result from the grain‐boundary clamp ing effect near the cubic‐tetragonal phase transition point.