Site-selective doping of transition metal cations into NaCo2O4

Yoshihiro Nojiri; Michitaka Ohtaki

doi:10.1109/ICT.2002.1190308

Site-selective doping of transition metal cations into NaCo₂O₄

Yoshihiro Nojiri, Michitaka Ohtaki

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

4 Citations (Scopus)

Abstract

We have investigated site-selective doping of Ni in order to experimentally explore the roles of the Na and Co sites of NaCO₂O₄. The selective doping is carried out by changing preparation procedures of the oxide. Cation "substitution" is intended by incorporating Ni(NO₃)₂ into a Co-deficient starting mixture of Na₂CO₃ and Co₃O₄ prior to the first heat treatment. Cation "exchange" is, on the other hand, carried out by heating a mixture of Ni(NO₃), and a single phase sample ofNaCo₂O₄, which has been prepared beforehand from a stoichiometric starting mixture. Comparison with control samples without addition of Ni(NO₃)₂ reveals that the "substituted" sample shows a significant decrease in the thermo power with keeping the electrical conductivity almost intact, while the "exchanged" sample shows the lower electrical conductivity with leaving the thermo power unchanged. These results strongly suggest that Ni cations occupy different sites in the Ni-doped samples; disturbing Co-Co spin exchange at the Co site, and compensating holes at the Na site.

Original language	English
Title of host publication	Proceedings ICT 2002
Subtitle of host publication	21st International Conference on Thermoelectrics
Publisher	Institute of Electrical and Electronics Engineers Inc.
Pages	234-237
Number of pages	4
ISBN (Electronic)	0780376838
DOIs	https://doi.org/10.1109/ICT.2002.1190308
Publication status	Published - 2002
Event	21st International Conference on Thermoelectrics, ICT 2002 - Long Beach, United States Duration: Aug 25 2002 → Aug 29 2002

Publication series

Name	International Conference on Thermoelectrics, ICT, Proceedings
Volume	2002-January

Other

Other	21st International Conference on Thermoelectrics, ICT 2002
Country/Territory	United States
City	Long Beach
Period	8/25/02 → 8/29/02

All Science Journal Classification (ASJC) codes

Condensed Matter Physics
Electrical and Electronic Engineering

Access to Document

10.1109/ICT.2002.1190308

Cite this

Nojiri, Y., & Ohtaki, M. (2002). Site-selective doping of transition metal cations into NaCo₂O₄. In Proceedings ICT 2002: 21st International Conference on Thermoelectrics (pp. 234-237). [1190308] (International Conference on Thermoelectrics, ICT, Proceedings; Vol. 2002-January). Institute of Electrical and Electronics Engineers Inc.. https://doi.org/10.1109/ICT.2002.1190308

Site-selective doping of transition metal cations into NaCo₂O₄. / Nojiri, Yoshihiro; Ohtaki, Michitaka.

Proceedings ICT 2002: 21st International Conference on Thermoelectrics. Institute of Electrical and Electronics Engineers Inc., 2002. p. 234-237 1190308 (International Conference on Thermoelectrics, ICT, Proceedings; Vol. 2002-January).

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

Nojiri, Y & Ohtaki, M 2002, Site-selective doping of transition metal cations into NaCo₂O₄. in Proceedings ICT 2002: 21st International Conference on Thermoelectrics., 1190308, International Conference on Thermoelectrics, ICT, Proceedings, vol. 2002-January, Institute of Electrical and Electronics Engineers Inc., pp. 234-237, 21st International Conference on Thermoelectrics, ICT 2002, Long Beach, United States, 8/25/02. https://doi.org/10.1109/ICT.2002.1190308

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abstract = "We have investigated site-selective doping of Ni in order to experimentally explore the roles of the Na and Co sites of NaCO2O4. The selective doping is carried out by changing preparation procedures of the oxide. Cation {"}substitution{"} is intended by incorporating Ni(NO3)2 into a Co-deficient starting mixture of Na2CO3 and Co3O4 prior to the first heat treatment. Cation {"}exchange{"} is, on the other hand, carried out by heating a mixture of Ni(NO3), and a single phase sample ofNaCo2O4, which has been prepared beforehand from a stoichiometric starting mixture. Comparison with control samples without addition of Ni(NO3)2 reveals that the {"}substituted{"} sample shows a significant decrease in the thermo power with keeping the electrical conductivity almost intact, while the {"}exchanged{"} sample shows the lower electrical conductivity with leaving the thermo power unchanged. These results strongly suggest that Ni cations occupy different sites in the Ni-doped samples; disturbing Co-Co spin exchange at the Co site, and compensating holes at the Na site.",

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AB - We have investigated site-selective doping of Ni in order to experimentally explore the roles of the Na and Co sites of NaCO2O4. The selective doping is carried out by changing preparation procedures of the oxide. Cation "substitution" is intended by incorporating Ni(NO3)2 into a Co-deficient starting mixture of Na2CO3 and Co3O4 prior to the first heat treatment. Cation "exchange" is, on the other hand, carried out by heating a mixture of Ni(NO3), and a single phase sample ofNaCo2O4, which has been prepared beforehand from a stoichiometric starting mixture. Comparison with control samples without addition of Ni(NO3)2 reveals that the "substituted" sample shows a significant decrease in the thermo power with keeping the electrical conductivity almost intact, while the "exchanged" sample shows the lower electrical conductivity with leaving the thermo power unchanged. These results strongly suggest that Ni cations occupy different sites in the Ni-doped samples; disturbing Co-Co spin exchange at the Co site, and compensating holes at the Na site.

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