Carrier type change induced by fluorine doping in spin-chain compound Ca 3 Co 2 O 6
The structural, magnetic, electrical, and thermoelectric properties of fluorine (F)-doped Ca 3 Co 2 O 6 were investigated systematically. Based on the use of X-ray diffraction, X-ray photoelectron spectroscopy spectra, and magnetic data, it was concluded that part of the Co 3+ ions at octahedral sit...
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Veröffentlicht in: | RSC advances 2017, Vol.7 (5), p.2745-2752 |
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Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | The structural, magnetic, electrical, and thermoelectric properties of fluorine (F)-doped Ca
3
Co
2
O
6
were investigated systematically. Based on the use of X-ray diffraction, X-ray photoelectron spectroscopy spectra, and magnetic data, it was concluded that part of the Co
3+
ions at octahedral sites would transfer into Co
2+
because of the substitution of F
−
for O
2−
. The induced Co
2+
ions are antiferromagnetically coupled with the nearest neighboring Co
3+
. The room-temperature resistivity decreases monotonously with the increase of fluorine (F)-doping content,
x
, and it is suggested that this is related to the increased carrier mobility. The resistivity curves of the samples with
x
≥ 0.4 show an anomaly at
T
* ∼ 320 K, which is considered to be related to the change of activation energy (
E
a
). The room temperature thermopower
S
300 K
changed from a positive value of 686.6 μV K
−1
to a negative value of −333.1 μV K
−1
as
x
increases from 0 to 0.4 and considering this with the Hall coefficient result, it is concluded that suitable F-doping in Ca
3
Co
2
O
6
can change the type of the majority of carriers from p to n with a decreased resistivity. The thermal conductivity,
κ
of the n-type samples is much larger than that of the p-type, and the
κ
of both the p-type and n-type samples decreases monotonously with increasing
x
. The anomaly of
κ
near
x
= 0.4 is suggested to originate from the decreased grain boundary scattering and the sudden decrease of
E
a
at the critical point of the carrier type change. |
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ISSN: | 2046-2069 2046-2069 |
DOI: | 10.1039/C6RA25052A |