TY - JOUR
T1 - Origin of appearance of PTCR properties in Bi-Sr-Ti-O system
AU - Sawaguchi, Takahiro
AU - Takamura, Hitoshi
AU - Tanaka, Terumi
AU - Homma, Motofumi
AU - Okada, Masuo
PY - 1996
Y1 - 1996
N2 - (Bi0.85Sr0.15)4(Ti0.95Nb 0.05)O12 shows a large positive temperature coefficient of resistivity (PTCR) properties of almost 4 orders of magnitude at about 543K. This temperature does not correspond to the Curie point of Bi4Ti3O12, but to the melting point of Bi metal. The microstructure of samples with or without showing PTCR properties observed by optical microscopy, showd the presence of Bi metal distributed in matrix. The various resistivity-temperature characteristics were obtained by controlling the distribution Bi metals in the matrix. Therefore, the new appearance of PTCR properties in Bi-Sr-Ti-O system would be related with the melting and solidification of Bi metal which is finely distributed in samples and isolated for each other. The equivalent electrical circuit for the samples were determind by complex impedance and modulus analysis. A model of this appearance of PTCR properties is proposed from these results as follows; Electrical current would flow in Bi metal at lower temperatures, but would not flow at higher temperatures. The resistivity of the sample at higher temperatures would be determined by matrix. Another RC component which acts only in the vicinity of PTCR temperature was also observed. This component may be due to the interface of Bi metals and the matrix.
AB - (Bi0.85Sr0.15)4(Ti0.95Nb 0.05)O12 shows a large positive temperature coefficient of resistivity (PTCR) properties of almost 4 orders of magnitude at about 543K. This temperature does not correspond to the Curie point of Bi4Ti3O12, but to the melting point of Bi metal. The microstructure of samples with or without showing PTCR properties observed by optical microscopy, showd the presence of Bi metal distributed in matrix. The various resistivity-temperature characteristics were obtained by controlling the distribution Bi metals in the matrix. Therefore, the new appearance of PTCR properties in Bi-Sr-Ti-O system would be related with the melting and solidification of Bi metal which is finely distributed in samples and isolated for each other. The equivalent electrical circuit for the samples were determind by complex impedance and modulus analysis. A model of this appearance of PTCR properties is proposed from these results as follows; Electrical current would flow in Bi metal at lower temperatures, but would not flow at higher temperatures. The resistivity of the sample at higher temperatures would be determined by matrix. Another RC component which acts only in the vicinity of PTCR temperature was also observed. This component may be due to the interface of Bi metals and the matrix.
KW - Bismuth-strontium-titanate-oxygen system
KW - Equivalent electrical circuit
KW - Impedance and modulus analysis
KW - New mechanism of PTCR properties
KW - Positive temperature coefficient of resistivity (PTCR) properties
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U2 - 10.2320/matertrans1989.37.426
DO - 10.2320/matertrans1989.37.426
M3 - Article
AN - SCOPUS:0030106194
SN - 0916-1821
VL - 37
SP - 426
EP - 429
JO - materials transactions, jim
JF - materials transactions, jim
IS - 3
ER -