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- Title
Electrical properties of MREGeO<sub>4</sub> (M = Li, Na, K; RE = rare earth) ceramics.
- Authors
Aung, Yan Lin; Nakayama, S.; Sakamoto, M.
- Abstract
Fourteen kinds of alkali-metal rare earth germanate ceramics, MREGeO4 (M = Li, Na, K; RE = rare earth), were synthesized and their electrical properties were investigated. The crystal structures of the major phases of MREGeO4 could be classified into four groups; hexagonal (apatite type), tetragonal, orthorhombic (olivine type) and orthorhombic (ß-K2SO4 type). The tetragonal group exhibited higher ionic conductivity than the other groups in the range 300 to 700°C. The highest conductivity was achieved for the LiNdGeO4 having a tetragonal structure (2.95 × 10-2 S cm-1 at 700°C). Analyses on the basis of the Nernst’s equation indicated that the two electron reaction associated with carbon dioxide molecule takes place at the detection electrode above 400°C regardless of the kind of electrolyte. The electromotive force, EMF, of the potentiometric CO2 gas sensors designed using MLaGeO4 (M = Li, Na, K) increased linearly with an increase in the logarithmic value of CO2 partial pressure, in accordance with the Nernst equation.
- Subjects
CERAMICS; ELECTRIC conductivity; RARE earth metal compounds; ALKALI metals; MICROSTRUCTURE; CRYSTALS; IONS; ELECTRONS
- Publication
Journal of Materials Science, 2005, Vol 40, Issue 1, p129
- ISSN
0022-2461
- Publication type
Article
- DOI
10.1007/s10853-005-5697-y