Full text of DOI:10.1007/BF03182824

elemental analysis, its ferroelectric and fatigue-free prop-
erties were investigated by measuring the electric hystere-
sis loop.
n-Pentylamine-intercalated
layered perovskite-type oxide
1
Experimental
1
1
1
HOU Wenhua , ZHONG Zhaohui , DING Weiping ,
Layered perovskite-type oxide, KSr Nb O (KSNO),
2
3
10
1
2
2
CHEN Yi , CHEN Xiaoyuan , ZHU Yongyuan
was synthesized at 1400ć using the ceramic method
from K CO , SrCO and Nb (KĩSrĩNb = 1.2ĩ2ĩ3,
molar ratio), and then exchanged with 6 molgL HNO at
2
&
MIN Naiben
2
3
3
2 5
O
ꢀ
1
1
. School of Chemistry and Chemical Engineering, Nanjing Univeristy,
Nanjing 210093, China;
3
1
2 3
80ć to get HSr Nb O10 (HSNO). The obtained HSNO
2
. National Laboratory of Solid State Microstructures, Nanjing Univer-
isty, Nanjing 210093, China
was finally reacted with 50% n-pentylamine ethanol solu-
Correspondence should be addressed to Hou Wenhua (e-mail:
qyan@nju.edu.cn)
tion at 120ć for 48 h to produce n-pentylamine-interca-
5 3 2 3 10
lated layered perovskite-type oxide, C H11NH -Sr Nb O
(
ASNO5). Apparatuses used were Shimadzu XD-3A
Abstract A novel n-pentylamine-intercalated layered
X-ray diffractometer, Nicolet 510P FT-IR spectrometer,
Bruker RFS-100 Raman spectrometer, and Perkin-Elmer
240C elemental analyzer. The measurements of electric
hysteresis loops and fatigue property were carried out
with RT6000HVS (High Voltage Test System, Radiant
Technologies Inc.). The pulverous samples were first
pressed into wafers with a 0.5-inch diameter under ~200
MPa, and then silver vapor was deposited onto both sides
of the wafers through the vacuum coating method.
5 3 2 3
perovskite-type oxide, C H11NH -Sr Nb O10, was prepared
and characterized by using XRD, FT-IR, Raman spec-
trascopy, and elemental analysis. It was shown that the in-
tercalated n-pentylamine adopted a bilayer formation with
some overlap and tilt, and the lattice of the perovskite layer
was distorted due to the intercalation of n-pentylamine. The
as-prepared sample gave clear electric hysteresis loop and
11
did not show fatigue after 10 switching circles, and there-
fore, could be considered as a new kind of fatigue-free ferro-
electric materials.
2
Results and discussion
Keywords: layered perovskite-type oxides, ferroelectricity, fatigue-
free.
Fig. 1. shows XRD patterns of KSNO, HSNO, and
ASNO. The d-value of (002) diffraction peak in KSNO
was 1.55 nm, suggesting a tri-layer structure of NbO
octahedrals in the perovskite layers. The layer thickness of
In recent years, scientists in the fields of chemistry,
physics and material science have been paying much at-
tention to the study on the manufacture of non-volatile
memories with high-speed access by using ferroelectric
6
ꢀ
Sr Nb O10 was calculated out to be 1.24 nm based on the
2 3
[6]
lattice parameters of KSNO . After intercalation, the
[
1ü 5]
oxides
. The traditional ferroelectric oxides fatigue
interlayer spacing was increased to 2.60 nm (2Tꢁꢁ= 3.4e).
easily and therefore, their application is limited. In 1995,
Scott et al. reported that some complex oxides such as
ꢀ
By subtracting the layer thickness of Sr
2
Nb
3
O
10 , the net
pillar height of the interlayered n-pentylammonium ions is
2 2 9 2 9 4 4 15
SrBi Ta O (SBT), SrBi TaNbO (SBTN) and SrBi Ta O ,
were ferroelectric oxides with good fatigue-free proper-
[
4]
ty .These oxides belong to a sort of layered perovskite-
type oxides whose structures consist of the perovskite
6 6
layers of NbO and/or TaO octahedrals, separated at in-
tervals by bismuth oxide planes. Considering the struc-
tural peculiarity of these oxides, we think that the ferro-
electricity comes from the perovskite layers, while the
fatigue-free property is mainly attributed to the buffering
effect of the bismuth oxide layers. If we can replace the
bismuth oxide layers with organic ammonium ions which
should have a better buffering effect between the
perovskite oxide layers, it is hopeful to get a new kind of
fatigue-free ferroelectric materials.
Based on the above consideration, we first prepared
layered perovskite-type oxide, KSr
ceramic method and then exchanged with HNO
HSr Nb 10, which was finally reacted with n-pen-
tylamine to obtain n-pentylamine-intercalated layered
perovskite-type oxide, C -Sr Nb 10. The as-pre-
2
Nb
3
O
10, by using the
3
to get
2
3
O
5
H11NH
3
2
3
O
pared sample was characterized by XRD, IR, Raman, and
Fig. 1. XRD patterns of KSNO (1), HSNO (2), and ASNO (3).
Chinese Science Bulletin Vol. 46 No. 8 April 2001
645

NOTES
Fig. 2. Raman spectra of KSNO (1), HSNO (2) and ASNO (3).
Fig. 3. IR spectra of KSNO (1), HSNO (2) and ASNO (3).
11
Fig. 4. The electric hysteresis loop before (a) and after (b) 10 switching circles.
+
[5]
1
.36 nm. The interlayered n-pentylammonium ions linked
H on the lattice vibration of the perovskite layers . For
ꢀ
1
with the perovskite layer by their hydrophilic amino
groups through hydrogen bond, while the hydrophobic
alkyl groups adopted a bilayer formation with some over-
lap and tilt, since the chain length of n-pentylammonium
ions is only 0.9 nm . Moreover, no characteristic (002)
diffraction of KSNO could be observed in the XRD pat-
tern of ASNO, indicating that the perovskite layers were
completely intercalated by n-pentylamine. C, H and N
elemenetal analysis results show a 53% exchange by
n-pentylammonium ions.
Figs. 2 and 3 show the Raman and IR spectra of the
corresponding samples, respectively. It can be seen in fig.
2
versal vibration of K , fully disappeared in HSNO and
ASNO, indicating the loss of the interlayered K ions after
sample ASNO, the peak at 931.9 cm even tended to split
into two peaks. The blue shift of the peak at 931.9 cm
ꢀ
1
was due to the distortion of the layer lattice after interca-
lation. The chain length of the intercalated organic amine
is so long that the interlayer spacing was increased to
some extent, therefore leading to the split of the peak. In
IR spectra, we can also see a corresponding blue shift of
the peak at 926 cm , and a new peak at 748 cm ap-
peared in sample ASNO5. All these characteristic features
of sample ASNO shown in the Raman and IR spectra
suggested that the lattice of the perovskite layers was dis-
torted after intercalation, thus broke up the superposition
of positive center and negative center, and finally induced
the ferroelectricity.
[
7]
ꢀ
1
ꢀ1
ꢀ
1
that the peak at 244.9 cm , which pertains to the trans-
+[8]
+
As shown in fig. 4(a), a clear electric hysteresis loop
was observed on sample ASNO. But the profile of the
loop is rough and the charge is low. We think that it is
because of the loose combination of non-oriented small
exchange with acid and intercalation of amine. Addition-
ally, a 24 cm blue shift of the peak at 931.9 cm after
acid exchange implied the strong effect of the interlayered
ꢀ
1
ꢀ1
646
Chinese Science Bulletin Vol. 46 No. 8 April 2001

and the National Natural Science Foundation of China (Grant No.
9903005).
crystals in the sample wafer. Then, it is reasonable to ex-
pect that the thin film of such material with a much more
highly ordered structure will show a higher charge.
Fig. 4(b) shows the electronic hysteresis loop of
ASNO after 10 switching circles, and still no fatigue was
observed. The interlayered pentylammonium ions may
minimize the interlayer stress upon polarization. It can
also be found that the profile became smooth and the
charge increased after switching, but the reason is still
unknown and needs to be further investigated.
2
References
11
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1
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3
Conclusions
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From the above discussion, a novel ferroelectric ox-
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type oxide, was prepared, and this material shows a good
fatigue-free property. Furthermore, if we select al-
kylamines with different chain lengths to be intercalated
into the perovskite layers, we can control the interlayer
spacing of the resulting materials, thus providing a new
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Acknowledgements The work was supported by the “973” Program
(Received July 31, 2000)
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647