新型层状钙钛矿K2La2/3Ta2O7与Li2La2/3Ta2O7的合成与结构解析
需积分: 10 76 浏览量
更新于2024-08-07
收藏 197KB PDF 举报
本文是一篇发表于2002年的学术论文，标题为《两种新型层状钙钛矿相 K2La2/3Ta2O7 和 Li2La2/3Ta2O7 的合成和晶体结构》（Synthesis and Crystal Structure of Two New Layered Perovskite Phases K2La2/3Ta2O7 and Li2La2/3Ta2O7）。作者是M. P. Crosnier-Lopez、F. Le Berre和J. L. Fourquet，来自法国勒芒的氟化物实验室，该实验室隶属于法国国家科研中心(U.M.R. C.N.R.S. 6010)的大学科学与技术学院（Université du Maine）。
研究者通过固体状态反应法成功合成并表征了两种新的层状钙钛矿相，即K2La2/3Ta2O7和Li2La2/3Ta2O7，这两者属于 Ruddlesden-Popper 家族，这是一种钙钛矿材料的特殊构型，其中La离子部分占据12-coordinated位点。钙钛矿的这种结构特性对于它们的电学和光学性质有重要影响。
论文的实验部分详细介绍了晶体结构的测定方法，包括粉末X射线衍射(powder X-ray diffraction, PXRD)和单晶X射线衍射(single crystal XRD)。对于K2La2/3Ta2O7，其空间群为I4/mmm，晶胞参数为a = 3.9679(1) Å 和 c = 22.0807(4) Å；而对于Li2La2/3Ta2O7，其空间群为P42/mnm，相应的晶胞参数为a = 5.564(3) Å 和 c = 18.134(5) Å。
这些数据不仅揭示了两种新化合物的微观结构，也为理解它们的物理性质提供了基础，如电导率、光吸收和可能的光电转换效率。由于钙钛矿材料在太阳能电池、光催化等领域具有广泛的应用前景，这类新型层状钙钛矿相的发现和研究对于推动相关技术的发展具有重要意义。
这篇论文不仅报告了新颖的化学合成方法，还展示了层状钙钛矿材料的新成员在晶体结构上的特点，为后续的材料设计和性能优化提供了重要的科学依据。
Synthesis and Crystal Structure of Two New Layered
Perovskite Phases K
2
La
2/3
Ta
2
O
7
and Li
2
La
2/3
Ta
2
O
7
M. P. Crosnier-Lopez*, F. Le Berre, and J. L. Fourquet
Le Mans/France, Laboratoire des Fluorures, U.M.R. C.N.R.S. 6010, Faculte
´
des Sciences et des Techniques, Universite
´
du Maine
Received May 15th, 2002.
Abstract. By solid state reaction two new layered perovskites have
been synthesized related to the Ruddlesden-Popper family,
K
2
La
2/3
Ta
2
O
7
and Li
2
La
2/3
Ta
2
O
7,
with La partial occupancy of the
12-coordinated site. The structures of K
2
La
2/3
Ta
2
O
7
and
Li
2
La
2/3
Ta
2
O
7
are respectively determined by powder X-ray diffrac-
tion and by single crystal XRD data : S.G. I4/mmm, Z ⫽ 2, a ⫽
3,9679(1) A
˚
and c ⫽ 22.0807(4) A
˚
for the K derivative and S.G.
P4
2
/mnm, Z ⫽ 4, a ⫽ 5.564(3) A
˚
and c ⫽ 18.134(5) A
˚
for the Li
Synthese und Kristallstrukturen der zwei neuen Schicht-Perowskit-Phasen
K
2
La
2/3
Ta
2
O
7
und Li
2
La
2/3
Ta
2
O
7
Inhaltsübersicht. Durch Festkörperreaktionen wurden zwei neue,
zur Ruddlesden-Popper-Familie gehörenden Schicht-Perowskite,
K
2
La
2/3
Ta
2
O
7
und Li
2
La
2/3
Ta
2
O
7
, dargestellt, in denen die Lanthan-
atome zum Teil die Plätze mit Zwölferkoordination besetzen. Die
Strukturen von K
2
La
2/3
Ta
2
O
7
bzw. Li
2
La
2/3
Ta
2
O
7
wurden durch
Röntgen-Pulverdiffraktogramme bzw. durch Einkristallstruktur-
analyse bestimmt. K
2
La
2/3
Ta
2
O
7
Raumgruppr I4/mmm, Z ⫽ 2, a ⫽
Introduction
Ruddlesden-Popper phases (RP), with the general formula
A’
2
[A
n⫺1
B
n
O
3n⫹1
], are of great interest for many of the
properties they exhibit, such as ion-exchange, intercalation
and ionic conductivity. The structure of these compounds
could be considered as derived from the perovskite struc-
ture with excess A’ atoms and oxygen in-between the BO
6
perovskite layers forming thus planar defects. In the formu-
lation, n defines the number of BO
6
octahedra forming per-
ovskite layers which are separated by A’ cations, A atoms
occupying the 12-coordinated perovskite cages. During our
efforts to synthesize such new phases, we have demonstrated
the formation of a new family of layered perovskites
Li
2
A
0.5n
B
n
O
3n⫹1
, [1] where various members can be formed
with the same set of A and B cations (A ⫽ La, Sr, Ca; B ⫽
Nb, Ta, Ti, Fe), which consequently leads to an increase in
A site deficiency in higher members.
In 1999, we reported the synthesis and the structure of
the new n ⫽ 2 member Li
2
SrTa
2
O
7
[1] and more recently,
* M.P. Crosnier-Lopez
Laboratoire des Fluorures, U.M.R. C.N.R.S. 6010,
Faculte
´
des Sciences et des Techniques, Universite
´
du Maine
72 085 Le Mans Cedex 9 ⫺ France
e-mail : marie-pierre.crosnier-lopez@univ-lemans.fr
Z. Anorg. Allg. Chem. 2002, 628, 2049⫺2056 WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002 0044⫺2313/02/628/2049⫺2056 $ 20.00⫹.50/0 2049
form. The supercell, √2a
p
, √2a
p
, c, observed for the latter phase
results from the kink of the octahedra inside the perovskite layers.
While Li
2
La
2/3
Ta
2
O
7
shows no water intercalation, a spontaneous
rapid hydration is observed for K
2
La
2/3
Ta
2
O
7
, leading to the
hydrate K
2
La
2/3
Ta
2
O
7
.2H
2
O.
Keywords: Lanthanum; Tantalum; Perovskites (layered); Structure
elucidation
3,9679(1) und c ⫽ 22,0807(4) A
˚
;Li
2
La
2/3
Ta
2
O
7
: Raumgruppe
P4
2
/mmm, Z ⫽ 4, a ⫽ 5,564(3) und c ⫽ 18,134(5) A
˚
. Die Über-
strukturzelle, √2a
p
, √2a
p
, c, die für die letztgenannte Phase beob-
achtet wurde, resultiert aus dem Abknicken der Oktaeder in den
Perowskitschichten. Während für Li
2
La
2/3
Ta
2
O
7
keine Intercalation
von Wasser beobachtet wird, zeigt K
2
La
2/3
Ta
2
O
7
schnelle Hydra-
tation, was zu K
2
La
2/3
Ta
2
O
7
·2H
2
O führt.
we have prepared and studied the layered RP phases,
K
2
SrTa
2
O
7
[2]; in both compounds, the A sites were fully
occupied by Sr
2⫹
cations. In order to test the stability of
these layered perovskite structures versus the vacancies
number in A sites, we substituted completely the Sr
2⫹
cat-
ions by La
3⫹
cations leading to a nominal vacancy rate of
1/3. In this paper, we present the synthesis and the struc-
tural determination of K
2
La
2/3
Ta
2
O
7
and Li
2
La
2/3
Ta
2
O
7
.
The first one, as already observed for many potassium lay-
ered perovskites, intercalates water leading to the hydrated
form K
2
La
2/3
Ta
2
O
7
.2H
2
O.
Experimental
Sample preparation
The synthesis of these two compounds requires very critical con-
ditions such as starting composition, temperature and cooling rate,
due both to the volatility of the lithium and potassium oxides at
higher temperatures and the formation of impurities (K
2
LaTa
5
O
15
[3] for K
2
La
2/3
Ta
2
O
7
and a mixture of LaTaO
4
[4], LiTaO
3
[5] and
Li
3
TaO
4
[6] for Li
2
La
2/3
Ta
2
O
7
). The two phases were prepared by
solid state reaction in air (total weight 1g) from stoichiometric
amounts of dry La
2
O
3
(Johnson Mattey, purity > 99.99%) (pre-
heated to 1000°C for 12h), Ta
2
O
5
(Johnson Mattey, purity >
99.85%), Li
2
CO
3
and K
2
CO
3
(Aldrich, purity > 99.99%). As often
mentioned for the synthesis of similar phases [1, 2, 7⫺10], an excess
下载后可阅读完整内容，剩余7页未读，立即下载
2021-05-09 上传
点击了解资源详情
点击了解资源详情
2021-03-04 上传
2021-03-31 上传
2021-02-06 上传
2021-03-29 上传
2021-06-29 上传
2021-06-29 上传
weixin_38682086
- 粉丝: 6
- 资源: 984
我的内容管理
展开
最新资源
- 前端协作项目：发布猜图游戏功能与待修复事项
- Spring框架REST服务开发实践指南
- ALU课设实现基础与高级运算功能
- 深入了解STK：C++音频信号处理综合工具套件
- 华中科技大学电信学院软件无线电实验资料汇总
- CGSN数据解析与集成验证工具集：Python和Shell脚本
- Java实现的远程视频会议系统开发教程
- Change-OEM: 用Java修改Windows OEM信息与Logo
- cmnd：文本到远程API的桥接平台开发
- 解决BIOS刷写错误28：PRR.exe的应用与效果
- 深度学习对抗攻击库：adversarial_robustness_toolbox 1.10.0
- Win7系统CP2102驱动下载与安装指南
- 深入理解Java中的函数式编程技巧
- GY-906 MLX90614ESF传感器模块温度采集应用资料
- Adversarial Robustness Toolbox 1.15.1 工具包安装教程
- GNU Radio的供应商中立SDR开发包：gr-sdr介绍
