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Improved Thermoelectric Characteristics of Si-Doped Misfit-Layered Cobaltite
Ist Teil von
Journal of electronic materials, 2011-05, Vol.40 (5), p.1042-1045
Ort / Verlag
Boston: Springer US
Erscheinungsjahr
2011
Link zum Volltext
Quelle
Springer LINK 全文期刊数据库
Beschreibungen/Notizen
The cobaltite Ca
3
Co
4
O
9+
δ
has shown large thermopower and is considered to be a good candidate for use as a thermoelectric material. The composition of Ca
3
Co
4
O
9+
δ
is better expressed as [Ca
2
CoO
3
][CoO
2
]
b
1/
b
2
with the misfit-layered structure featuring different periodicities along the
b
axis, with
b
1
referring to the
b
-axis length of the NaCl-type [Ca
2
CoO
3
] sublattice and
b
2
referring to the
b
-axis length of the [CoO
2
] sublattice. The crystal structure of Ca
3
Co
4
O
9+
δ
can be viewed as being of two subsystems, i.e., the distorted NaCl-type [Ca
2
CoO
3
] sublattice and the CdI
2
-type [CoO
2
] sublattice, alternately stacked along the
c
-axis. In this paper, we report measurements of the electrical resistivity and Seebeck coefficient for a series of misfit-layered oxides Ca
3
Co
4−
x
Si
x
O
9+
δ
prepared by solid-state reaction. Structural parameters are refined with the superspace group X2/m(0β0)s0 using powder x-ray diffraction data. With partial substitution of Si
4+
for Co
3+
, the resistivity decreases, while the thermopower increases simultaneously. These results indicate that partial substitution of Si
4+
improves the thermoelectric characteristics of Ca
3
Co
4
O
9+
δ
.