p-Type electronic conductivity, oxygen permeability and stability of La2Ni0.9Co0.1O4+δ

Aleksey A. Yaremchenko; Vladislav V. Kharton; Mikhail V. Patrakeev; Jorge R. Frade

doi:10.1039/B300357D

p-Type electronic conductivity, oxygen permeability and stability of La₂Ni_0.9Co_0.1O_4+δ†

Aleksey A. Yaremchenko,^a Vladislav V. Kharton,‡*^ab Mikhail V. Patrakeev^ac and Jorge R. Frade^a

* Corresponding authors

^a Department of Ceramics and Glass Engineering, CICECO, University of Aveiro, 3810-193 Aveiro, Portugal
E-mail: kharton@cv.ua.pt
Fax: +351-234-425300
Tel: +351-234-370263

^b Institute of Physicochemical Problems, Belarus State University, 14 Leningradskaya Str., 220050 Minsk, Republic of Belarus

^c Institute of Solid State Chemistry, Ural Division of RAS, 91 Pervomaiskaya Str., Ekaterinburg 620219, Russia

Abstract

The oxygen permeability, total conductivity and Seebeck coefficient of La₂Ni_0.9Co_0.1O_4+δ were studied in the oxygen partial pressure range of 10⁻¹⁶ Pa to 50 kPa at 973–1223 K. The conductivity of La₂Ni_0.9Co_0.1O_4+δ is predominantly p-type electronic within the whole p(O₂) range in which the K₂NiF₄-type structure exists. Thermally-activated mobility, the values of which are 0.02–0.08 cm² V⁻¹ s⁻¹, and the p(O₂) dependencies of electron-hole transport suggest a small-polaron conduction mechanism. Oxygen permeability of dense La₂Ni_0.9Co_0.1O_4+δ membranes, with an apparent activation energy of 192 kJ mol⁻¹ in oxidising conditions, is limited by both bulk ionic conductivity and the surface exchange rate. The role of surface processes in limiting permeation is also significant under air/H₂–H₂O gradients and increases with decreasing temperature. The stability boundary of the La₂Ni_0.9Co_0.1O_4+δ phase at low oxygen pressures is similar to that of undoped lanthanum nickelate, which allows stable operation of nickelate membranes under high oxygen chemical potential gradients, such as air/10% H₂–90% N₂, at 973 K. At temperatures above 1000 K, the decomposition products form blocking layers on the membrane surface causing degradation of the membrane performance with time. The average thermal expansion coefficient of La₂Ni_0.9Co_0.1O_4+δ ceramics, calculated from dilatometric data in air, is 12.8 × 10⁻⁶ K⁻¹ at 400–1265 K.

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Article information

DOI: https://doi.org/10.1039/B300357D
Article type: Paper
Submitted: 13 Jan 2003
Accepted: 11 Mar 2003
First published: 27 Mar 2003

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J. Mater. Chem., 2003,13, 1136-1144

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p-Type electronic conductivity, oxygen permeability and stability of La₂Ni_0.9Co_0.1O_4+δ

A. A. Yaremchenko, V. V. Kharton, M. V. Patrakeev and J. R. Frade, J. Mater. Chem., 2003, 13, 1136 DOI: 10.1039/B300357D

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