Local property measurement in PTC thermistors

J. Seaton; C. Leach

doi:10.1016/S1359-6454(03)00387-2

Local property measurement in PTC thermistors

J. Seaton, C. Leach

Research output: Contribution to journal › Article › peer-review

Abstract

The local electrical properties of a positive temperature coefficient (PTC) thermistor based on donor doped BaTiO3 with additions of Sr, Pb and Ca, have been characterised and correlated with the results of compositional, microstructural and crystallographic analyses. Wavelength dispersive spectroscopy showed a significant depletion in lead near the pellet surface, caused by volatilisation during sintering. Compensation for the lead loss was principally by Ba substitution, with only a small increase in the levels of Ca and Sr. Local resistance-temperature (R-T) measurements showed a slight reduction in switching temperature, together with an increase in the pre-switching resistance, within the lead depleted zone. Electron backscatter pattern (EBSP) analysis revealed a significant proportion of Σ=3 and 9 grain boundaries, which are reported to be PTC inactive, in the microstructure. The proportion of Σ=3 grain boundaries was significantly higher in the lead-depleted zone than in the bulk of the pellet. © 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Original language	English
Pages (from-to)	6027-6034
Number of pages	7
Journal	Acta Materialia
Volume	51
Issue number	20
DOIs	https://doi.org/10.1016/S1359-6454(03)00387-2
Publication status	Published - 8 Dec 2003

Keywords

Coincidence lattice
Electrical conductivity
Electroceramics
Electron backscattering patterns
Interfaces

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10.1016/S1359-6454(03)00387-2

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title = "Local property measurement in PTC thermistors",

abstract = "The local electrical properties of a positive temperature coefficient (PTC) thermistor based on donor doped BaTiO3 with additions of Sr, Pb and Ca, have been characterised and correlated with the results of compositional, microstructural and crystallographic analyses. Wavelength dispersive spectroscopy showed a significant depletion in lead near the pellet surface, caused by volatilisation during sintering. Compensation for the lead loss was principally by Ba substitution, with only a small increase in the levels of Ca and Sr. Local resistance-temperature (R-T) measurements showed a slight reduction in switching temperature, together with an increase in the pre-switching resistance, within the lead depleted zone. Electron backscatter pattern (EBSP) analysis revealed a significant proportion of Σ=3 and 9 grain boundaries, which are reported to be PTC inactive, in the microstructure. The proportion of Σ=3 grain boundaries was significantly higher in the lead-depleted zone than in the bulk of the pellet. {\textcopyright} 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.",

keywords = "Coincidence lattice, Electrical conductivity, Electroceramics, Electron backscattering patterns, Interfaces",

author = "J. Seaton and C. Leach",

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doi = "10.1016/S1359-6454(03)00387-2",

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journal = "Acta Materialia",

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TY - JOUR

T1 - Local property measurement in PTC thermistors

AU - Seaton, J.

AU - Leach, C.

PY - 2003/12/8

Y1 - 2003/12/8

N2 - The local electrical properties of a positive temperature coefficient (PTC) thermistor based on donor doped BaTiO3 with additions of Sr, Pb and Ca, have been characterised and correlated with the results of compositional, microstructural and crystallographic analyses. Wavelength dispersive spectroscopy showed a significant depletion in lead near the pellet surface, caused by volatilisation during sintering. Compensation for the lead loss was principally by Ba substitution, with only a small increase in the levels of Ca and Sr. Local resistance-temperature (R-T) measurements showed a slight reduction in switching temperature, together with an increase in the pre-switching resistance, within the lead depleted zone. Electron backscatter pattern (EBSP) analysis revealed a significant proportion of Σ=3 and 9 grain boundaries, which are reported to be PTC inactive, in the microstructure. The proportion of Σ=3 grain boundaries was significantly higher in the lead-depleted zone than in the bulk of the pellet. © 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

AB - The local electrical properties of a positive temperature coefficient (PTC) thermistor based on donor doped BaTiO3 with additions of Sr, Pb and Ca, have been characterised and correlated with the results of compositional, microstructural and crystallographic analyses. Wavelength dispersive spectroscopy showed a significant depletion in lead near the pellet surface, caused by volatilisation during sintering. Compensation for the lead loss was principally by Ba substitution, with only a small increase in the levels of Ca and Sr. Local resistance-temperature (R-T) measurements showed a slight reduction in switching temperature, together with an increase in the pre-switching resistance, within the lead depleted zone. Electron backscatter pattern (EBSP) analysis revealed a significant proportion of Σ=3 and 9 grain boundaries, which are reported to be PTC inactive, in the microstructure. The proportion of Σ=3 grain boundaries was significantly higher in the lead-depleted zone than in the bulk of the pellet. © 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

KW - Coincidence lattice

KW - Electrical conductivity

KW - Electroceramics

KW - Electron backscattering patterns

KW - Interfaces

U2 - 10.1016/S1359-6454(03)00387-2

DO - 10.1016/S1359-6454(03)00387-2

M3 - Article

SN - 1873-2453

VL - 51

SP - 6027

EP - 6034

JO - Acta Materialia

JF - Acta Materialia

IS - 20

ER -

Local property measurement in PTC thermistors

Abstract

Keywords

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