Doping effects on the physicochemical and electrochemical properties of lanthanum manganite

Citation
La. Tikhonova et al., Doping effects on the physicochemical and electrochemical properties of lanthanum manganite, INORG MATER, 36(10), 2000, pp. 1036-1042
Citations number
15
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Journal title
INORGANIC MATERIALS
ISSN journal
00201685 → ACNP
Volume
36
Issue
10
Year of publication
2000
Pages
1036 - 1042
Database
ISI
SICI code
0020-1685(200010)36:10<1036:DEOTPA>2.0.ZU;2-O
Abstract
The structural, thermal, electrical, and electrochemical properties of La0. 7Ca0.3Mn1-x(Co,Ni)(x)O-3 and La0.6Sr0.4Mn1-x(Co,Ni)(x)O-3 (x = 0, 0.02, 0.0 5, 0.1) electrode materials were studied. Doping of the cubic perovskites w ith Co or Ni increases the fraction of Mn4+ ions, up to 49% in La0.7Ca0.3Mn 0.9Co0.1O3 and 57% in La0.6Sr0.4Mn0.95Co0.05O3. The 300-K conductivity of L a0.7Ca0.3Mn1-xNixO3 passes through a maximum at x = 0.05, while that of La0 .6Sr0.4Mn1-xCoxO3 decreases steadily with increasing x. In the range 300-11 00 K, the conductivity of the Ca-containing manganites exhibits semiconduct ing behavior, whereas that of the Sr-containing materials shows metallic be havior. No phase transformations were detected in this temperature range. I n the four systems, the thermal-expansion coefficients are virtually indepe ndent of x. In both undoped and doped electrode materials, the resistance p arameter pld of electrode layers on solid-electrolyte substrates shows semi conducting behavior at temperatures from 300 to 1100 K and oxygen partial p ressures from 10(2) to 10(5) Pa. With increasing oxygen partial pressure or electrode-layer thickness (d = 15-100 mg/cm(2)), rho /d decreases. The opt imal electrode-layer thickness is found to be about 50 mg/cm(2). The introd uction of Co or Ni into the electrode materials decreases the polarization resistance of the electrode layer in gas/electrode/electrolyte systems. Com positions ensuring the lowest polarization resistance were found.