硅酸盐学报

高温还原La_1-_xSr_xCr_0.5Mn_0.5O₃钙钛矿的晶体结构研究

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陈冬梅 ¹^,³ , 徐序 ¹^,³ , 罗凌虹 ¹^,³ , 王乐莹 ¹^,³ , 程亮 ²^,³ , 余剑峰 ¹^,³ , 杭琪 ¹^,³

硅酸盐学报 | 氢能储能专题—研究论文 2024,52(6): 1832-1840

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硅酸盐学报 |氢能储能专题—研究论文 2024 , 52 (6) : 1832 -1840

高温还原La_1-_xSr_xCr_0.5Mn_0.5O₃钙钛矿的晶体结构研究

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陈冬梅¹^,³, 徐序¹^,³, 罗凌虹¹^,³, 王乐莹¹^,³, 程亮²^,³, 余剑峰¹^,³, 杭琪¹^,³

作者信息

^1．景德镇陶瓷大学材料科学与工程学院，江西景德镇 333403

^2．国家日用及建筑陶瓷工程技术研究中心，江西景德镇 333001

^3．景德镇陶瓷大学江西省燃料电池材料与器件重点实验室，江西景德镇 333001

通讯作者:

徐序（1980—），男，博士，副教授。

作者简介:

陈冬梅（1998—），女，硕士研究生。

Crystal Structure of La_1-_xSr_xCr_0.5Mn_0.5O₃ Perovskites Reduced at High-Temperature

Dongmei CHEN¹^,³, Xu XU¹^,³, Linghong LUO¹^,³, Leying WANG¹^,³, Liang CHENG²^,³, Jianfeng YU¹^,³, Qi HANG¹^,³

Affiliations

^1.School of Materials Science and Engineering, Jingdezhen Ceramic University, Jingdezhen 333403, Jiangxi, China

^2.National Engineering Research Center for Domestic & Building Ceramics, Jingdezhen 333001, Jiangxi, China

^3.Jiangxi Provincial Key Laboratory of Fuel Cell Material and Devices, Jingdezhen Ceramic University, Jingdezhen 333001, Jiangxi, China

Corresponding Author:

XU Xu (1980-), male, Ph.D., Associate Professor. E-mail: xuxu_80@163.com

CHEN Dongmei (1998-), female, Master candidate. E-mail: 2579839041@qq.com

出版时间: 2024-06-20 doi: 10.14062/j.issn.0454-5648.20240037

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摘要

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La_1-_xSr_xCr_0.5Mn_0.5O₃（LSCM）是一种因具有优良综合性能而受到广泛关注的固体氧化物电池（SOC）钙钛矿型燃料电极材料，但其在SOC工况下受Sr含量、温度、气氛等因素影响时的结构稳定性方面仍缺乏系统深入的研究。采用柠檬酸溶胶-凝胶法制备了不同Sr含量的LSCM粉体，对各样品在不同温度下还原处理后的晶体结构和晶型转变情况进行了XRD表征，发现经过还原热处理LSCM会发生菱方相和正交相之间的转变。详细探讨了LSCM的晶体结构随Sr含量和还原热处理温度变化的规律，并结合Fourier红外光谱和X射线光电子能谱表征以及第一性原理计算，从元素价态、金属—氧化学键强度、晶体结合能以及Jahn-Teller畸变等角度出发分析了Sr掺杂对体系结构稳定性的影响，阐明了与Sr含量及还原热处理温度相关的LSCM晶型转变机制。

关键词

固体氧化物电池 / 燃料电极 / 钙钛矿 / 相变 / Jahn-Teller畸变

Abstract

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Introduction

La_1-_xSr_xCr_0.5Mn_0.5O₃ (LSCM) perovskite as a SOC fuel electrode material has attracted much attention due to its excellent comprehensive performance. However, there is still a lack of systematic and in-depth research on the its structural stability that is affected by some factors such as Sr content, temperature, and atmosphere under operating conditions of SOC. In particular, previous work indicate that this material exhibits different electrode performances and crystal structures under Sr-free and Sr-containing conditions, having the Sr content impact on its structural stability and electrochemical performance. Therefore, this paper was to analyze the crystal structures of La_1-_xSr_xCr_0.5Mn_0.5O₃ heat-treated in a reducing atmosphere at elevated temperatures from 500 ℃ to 1 000 ℃. In addition, the mechanism of crystal structural transformation of LSCM in a high-temperature reducing atmosphere was also discussed.

Methods

The LSCM precursors with different Sr contents (i.e., x of 0, 0.1, 0.2, and 0.3) were prepared by a citric acid sol-gel method. The precursors were calcined into LSCM powders in a muffle furnace at 1100 ℃. The LSCM powders were then thermally reduced in a reducing atmosphere at 500 ℃-1 000 ℃. After reduction, the phase transformations of each sample were characterized by X-ray diffraction (XRD). The lattice constants of the samples were calculated based on the Rietveld method using a software named Rietica. In addition, the first-principles calculations, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were also performed to reveal the effects of Sr content and reduction heat treatment on the crystal transformation of LSCM.

Results and discussion

The samples with different Sr contents were calcined in air at 1 100 ℃. A single trigonal phase appears when the Sr contents x≤0.2, while a small amount of SrCrO₄ phase occurs besides the perovskite phase when x=0.3. After reduction at elevated temperatures, the sample with x of 0 transforms from a trigonal phase to an orthorhombic phase, and its crystal structure is relatively stable according to the fact that there are no other phases formed with increasing the reduction temperature. The XRD patterns of LCM samples reduced at different temperatures are analyzed using the Rietveld method. The results show that the unit cell volume of the reduced perovskite samples increases with the increase of heat treatment temperature from 700 ℃ to 1 000 ℃. However, the unit cell volume of the sample reduced at 600 ℃ is smaller than that at 500 ℃. This is because the sample begin to lose a considerable amount of oxygen at 500-600 ℃ during the reduction heat treatment, leading to a significant change in the shape of the crystal unit cell. For the samples with x of 0.1 and 0.2, trigonal and orthorhombic phases co-exist, and the proportion of trigonal phase increases with increasing x value but decreases with increasing reduction temperature. A layered perovskite oxide phase of (La,Sr)₂MnO₄ appears in the sample with x of 0.2 when the reduction temperature increases to 900 ℃, indicating that this sample has a poorer structural stability, compared with the sample with x of 0.1. According to the XPS results, compared with the LCM without Sr, the Mn³⁺ concentration in the reduced LSCM is relatively low as the Sr content increases, which can alleviate the Jahn-Teller distortion. Therefore, LSCM tends to form a trigonal phase, while LCM undergoes a more significant Jahn-Teller distortion, making it tends to transform into a more stable structure of orthorhombic phase than trigonal phase. The FTIR spectra reveal that the Mn/Cr—O bond energy increases in the LSCM perovskite with the increase of Sr content. The lattice parameters of each sample are calculated using the Rietveld method based on the XRD data, and subsequently the lengths of Mn/Cr-O bonds of each crystal are calculated. The results demonstrate that the length of Mn/Cr—O bond in the crystals decreases with the increase of Sr content, which is consistent with the conclusion derived from the FTIR spectra. However, the first-principles calculations confirm that the binding energy of the crystal of LSCM gradually increases with the increase of Sr content. Therefore, in summary, the existence of trigonal phase and the increase of binding energy caused by Sr doping jointly lead to the fact that the structural stability of Sr-containing LSCM perovskite is lower than that of Sr-free LCM under high-temperature reduction atmosphere conditions.

Conclusions

The structural transformation process and regularity of the LSCM perovskites under high-temperature reducing atmosphere were mainly controlled by the Jahn-Teller distortion, which depended on the concentration of Mn³⁺. The LCM without Sr underwent a more significant Jahn-Teller distortion, making it form an orthorhombic phase. The increase of Sr content mitigated the Jahn-Teller distortion, making the Sr-containing LSCM perovskites more likely to form a trigonal phase as well as possess an increased binding energy, thus reducing the structural stability of LSCM.

Key words

solid oxide cells / fuel electrode / perovskite / phase transition / Jahn-Teller distortion

引用本文

陈冬梅, 徐序, 罗凌虹, 王乐莹, 程亮, 余剑峰, 杭琪. 高温还原La_1-_xSr_xCr_0.5Mn_0.5O₃钙钛矿的晶体结构研究. 硅酸盐学报, 2024 , 52 (6) : 1832 -1840 . DOI: 10.14062/j.issn.0454-5648.20240037

Dongmei CHEN, Xu XU, Linghong LUO, Leying WANG, Liang CHENG, Jianfeng YU, Qi HANG. Crystal Structure of La_1-_xSr_xCr_0.5Mn_0.5O₃ Perovskites Reduced at High-Temperature[J]. Journal of the Chinese Ceramic Society, 2024 , 52 (6) : 1832 -1840 . DOI: 10.14062/j.issn.0454-5648.20240037

基金

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国家自然科学基金(51762026; 51802132)
江西省自然科学基金重点项目(20224ACB204010)
江西省教育厅科技落地计划(KJLD13072)
江西省教育厅科技项目(GJJ2201009; GJJ2201010)
景德镇市科技计划项目(2023GY001-06)
景德镇市科技计划项目(20234ST005)

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2024年第52卷第6期

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文章信息

doi: 10.14062/j.issn.0454-5648.20240037

接收时间：2024-01-15
首发时间：2026-10-22
出版时间：2024-06-20

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出版历史

收稿日期：2024-01-15
修回日期：2024-02-01

基金

国家自然科学基金(51762026; 51802132)

江西省自然科学基金重点项目(20224ACB204010)

江西省教育厅科技落地计划(KJLD13072)

江西省教育厅科技项目(GJJ2201009; GJJ2201010)

景德镇市科技计划项目(2023GY001-06)

景德镇市科技计划项目(20234ST005)

作者信息

^1．景德镇陶瓷大学材料科学与工程学院，江西景德镇 333403

^2．国家日用及建筑陶瓷工程技术研究中心，江西景德镇 333001

^3．景德镇陶瓷大学江西省燃料电池材料与器件重点实验室，江西景德镇 333001

通讯作者:

徐序（1980—），男，博士，副教授。

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https://castjournals.cast.org.cn/joweb/gsyxb/CN/10.14062/j.issn.0454-5648.20240037

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2种不同金属材料的力学参数

科 Family	属数 Number of genus	种数 Number of species	占总种数比例 Percentage of total species (%)	属 Genus	种数 Number of species	占总种数比例 Percentage of total species (%)
鹅膏菌科Amanitaceae	2	11	5.26	鹅膏菌属 Amanita	10	4.78
小菇科 Mycenaceae	2	12	5.74	丝盖伞属 Inocybe	5	2.39
多孔菌科 Polyporaceae	8	14	6.70	蜡蘑属 Laccaria	5	2.39
红菇科 Russulaceae	3	23	11.00	小皮伞属 Marasmius	6	2.87
				小菇属 Mycena	11	5.26
				光柄菇属 Pluteus	5	2.39
				红菇属 Russula	17	8.13
				栓菌属 Trametes	5	2.39

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