Electrical conductivity of Ni–YSZ composites: Variants and redox cycling

Publication: Research - peer-reviewJournal article – Annual report year: 2012

Standard

Electrical conductivity of Ni–YSZ composites: Variants and redox cycling. / Pihlatie, Mikko; Kaiser, Andreas; Mogensen, Mogens Bjerg.

In: Solid State Ionics, Vol. 222-223, 2012, p. 38-46.

Publication: Research - peer-reviewJournal article – Annual report year: 2012

Harvard

APA

CBE

MLA

Vancouver

Author

Pihlatie, Mikko; Kaiser, Andreas; Mogensen, Mogens Bjerg / Electrical conductivity of Ni–YSZ composites: Variants and redox cycling.

In: Solid State Ionics, Vol. 222-223, 2012, p. 38-46.

Publication: Research - peer-reviewJournal article – Annual report year: 2012

Bibtex

@article{8937ec8b0ce746b09aa520d251342ed1,
title = "Electrical conductivity of Ni–YSZ composites: Variants and redox cycling",
keywords = "SOFC, Ni–YSZ, Electrical conductivity, Redox stability, Ni particle growth, Master sintering curve",
publisher = "Elsevier BV North-Holland",
author = "Mikko Pihlatie and Andreas Kaiser and Mogensen, {Mogens Bjerg}",
year = "2012",
doi = "10.1016/j.ssi.2012.06.021",
volume = "222-223",
pages = "38--46",
journal = "Solid State Ionics",
issn = "0167-2738",

}

RIS

TY - JOUR

T1 - Electrical conductivity of Ni–YSZ composites: Variants and redox cycling

A1 - Pihlatie,Mikko

A1 - Kaiser,Andreas

A1 - Mogensen,Mogens Bjerg

AU - Pihlatie,Mikko

AU - Kaiser,Andreas

AU - Mogensen,Mogens Bjerg

PB - Elsevier BV North-Holland

PY - 2012

Y1 - 2012

N2 - Short-term changes in the electrical conductivity of different Ni–YSZ composites (cermets) were measured by an in-situ 4-point DC technique. The isothermal reduction was carried out in dry, humidified or wet hydrogen at temperatures from 600 to 850°C. The cermets reduced at 600°C showed a stable conductivity of about 1100S/cm, which increased to an enhanced ~2000S/cm upon re-oxidation and subsequent re-reduction cycling at the same temperature. At 850°C, a rapid initial conductivity loss was observed; upon re-reduction after the re-oxidation both the conductivity and its loss rate were largely the same as in the initial reduction. The presence of steam had an accelerating effect on the conductivity loss at 850°C. In addition to cermets with a typical microstructure, different modified microstructures and compositions were tested. In the modified cermets, Al, Mg, and Ce were used as Ni dopants alongside with undoped Ni. Scanning electron microscopy of cermets reduced in different conditions showed increasing particle size and loss of metal-to-metal percolation in the samples reduced at higher temperatures, and a very fine microstructure in the high conductivity sample re-oxidised at 600°C. Short-term conductivity changes due to microstructural changes in both the standard and modified cermets with different Ni doping were compared by re-oxidation at 600°C and subsequent thermal excursions up to 1000°C by normalising the conductivity to a constant temperature. Modified cermets show reduced conductivity loss on both isothermal heating and high temperature ramping. Most stable cermets were the ones with undoped NiO and modified microstructure, as well as modified microstructures using Ti and Mg, or Ce secondary oxide coatings. Master sintering curve approach was successfully implemented to analyse the conductivity loss data. The MSC analysis yielded apparent activation energies for Ni sintering within the composite of 375kJ/mol when heated in dry H2 and 440kJ/mol when under wet H2.

AB - Short-term changes in the electrical conductivity of different Ni–YSZ composites (cermets) were measured by an in-situ 4-point DC technique. The isothermal reduction was carried out in dry, humidified or wet hydrogen at temperatures from 600 to 850°C. The cermets reduced at 600°C showed a stable conductivity of about 1100S/cm, which increased to an enhanced ~2000S/cm upon re-oxidation and subsequent re-reduction cycling at the same temperature. At 850°C, a rapid initial conductivity loss was observed; upon re-reduction after the re-oxidation both the conductivity and its loss rate were largely the same as in the initial reduction. The presence of steam had an accelerating effect on the conductivity loss at 850°C. In addition to cermets with a typical microstructure, different modified microstructures and compositions were tested. In the modified cermets, Al, Mg, and Ce were used as Ni dopants alongside with undoped Ni. Scanning electron microscopy of cermets reduced in different conditions showed increasing particle size and loss of metal-to-metal percolation in the samples reduced at higher temperatures, and a very fine microstructure in the high conductivity sample re-oxidised at 600°C. Short-term conductivity changes due to microstructural changes in both the standard and modified cermets with different Ni doping were compared by re-oxidation at 600°C and subsequent thermal excursions up to 1000°C by normalising the conductivity to a constant temperature. Modified cermets show reduced conductivity loss on both isothermal heating and high temperature ramping. Most stable cermets were the ones with undoped NiO and modified microstructure, as well as modified microstructures using Ti and Mg, or Ce secondary oxide coatings. Master sintering curve approach was successfully implemented to analyse the conductivity loss data. The MSC analysis yielded apparent activation energies for Ni sintering within the composite of 375kJ/mol when heated in dry H2 and 440kJ/mol when under wet H2.

KW - SOFC

KW - Ni–YSZ

KW - Electrical conductivity

KW - Redox stability

KW - Ni particle growth

KW - Master sintering curve

U2 - 10.1016/j.ssi.2012.06.021

DO - 10.1016/j.ssi.2012.06.021

JO - Solid State Ionics

JF - Solid State Ionics

SN - 0167-2738

VL - 222-223

SP - 38

EP - 46

ER -