兰州大学机构库 >核科学与技术学院
钙钛矿氧化物的辐照效应研究:层状结构与结构因子的影响
Alternative TitleRadiation effects of perovskite oxides: the role of layered structure and structural factors
王梦辉
Subtype硕士
Thesis Advisor杨冬燕
2023-05-27
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name工学硕士
Degree Discipline核技术及应用
Keyword钙钛矿 perovskite 离子束辐照 ion beam irradiation 层状结构 layered structure 结构因子 structural factor
Abstract

钙钛矿由于具有优异的物理化学稳定性和抗辐照性能被看作是新一代的高放射性核废物候选固化基材。高放射性核废物具有极高的放射性,这对固化体的辐照稳定性提出了较高的要求。如何提高及预测钙钛矿的抗辐照性能具有重要意义。本论文以钙钛矿氧化物的辐照效应研究为基础,开展了两方面的研究工作:(1)基于Ruddlesden-Popper (RP)相(SrTiO3)nSrO (n=1, 2, 3, ∞)钙钛矿首次系统地研究了层状结构对钙钛矿材料的辐照行为的影响;(2)基于ABO3 (A=Ca, Sr, Ba; B=Ti, Zr)钙钛矿探究了钙钛矿氧化物的辐照稳定性与结构因子之间的关联。

本论文的第一部分工作是基于RP相(SrTiO3)nSrO (n=1, 2, 3, ∞)探究层状结构对材料抗辐照性能的影响。通过高温固相法制备了RP相(SrTiO3)nSrO (n=1, 2, 3, ∞)钙钛矿样品,利用X射线衍射技术、激光共聚焦拉曼光谱、透射电子显微镜和扫描电子显微镜对材料的微观结构进行了表征,结果表明所制备的样品物相单一,无杂质;(SrTiO3)nSrO (n=∞)即SrTiO3为立方相(晶格常数a=b=c),(SrTiO3)nSrO (n=1, 2, 3)为四方相(晶格常数a=b≠c);通过透射电子显微镜测得的晶面间距与X射线衍射测得的结果吻合,样品结晶度高;SrTiO3和(SrTiO3)nSrO (n=1, 2, 3)的表面形貌分别为球状和棒条状,这与其立方相和四方相的晶体结构一致;(SrTiO3)nSrO (n=1, 2, 3)的晶格常数c值随n值的增加线性增长,符合RP相(SrTiO3)nSrO (n=1, 2, 3)内部[SrO]和[SrTiO3]结构单元有序堆叠的层状结构特征。

采用3 MeV Xe离子在室温和高温下分别对样品进行辐照以探究样品在离子束辐照下的结构演化行为,通过掠入射X射线衍射技术对辐照前后样品的结构进行表征。在室温3 MeV Xe离子辐照下,(SrTiO3)nSrO (n=1, 2, 3, ∞)钙钛矿样品产生不同程度的晶格肿胀和非晶化。对于同一组分的样品,随着离子注量的增加,晶胞体积肿胀率和非晶化含量逐渐增大。同一离子注量下,随着n值的增加(RP相SrO层密度的减少),材料的抗辐照性能增强。在350 ℃和650 ℃ 3 MeV Xe离子辐照下,SrTiO3始终保持原有晶体结构,而(SrTiO3)nSrO (n=1, 2, 3)随温度和离子注量的增加相分解为SrTiO3和SrO;在高温离子束辐照下,(SrTiO3)nSrO (n=1, 2, 3, ∞)的抗辐照性能也是随n值的增加而增强。对未辐照的样品和室温辐照后的样品在350 ℃下退火1 h,结果表明高温辐照下(SrTiO3)nSrO (n=1, 2, 3)相变是温度和辐照协同效应的结果。该部分研究工作明晰了层状结构对RP相(SrTiO3)nSrO (n=1, 2, 3, ∞)钙钛矿材料在室温及高温离子束辐照下的结构演化行为的影响。

本论文的另一项工作研究了钙钛矿氧化物的抗辐照性能与结构因子之间的关联。通过高温固相法制备了五种具有不同结构因子的ABO3 (A=Ca, Sr, Ba; B=Ti, Zr)钙钛矿,运用X射线衍射技术和扫描电子显微镜对材料的微观结构进行了表征,结果表明各样品物相单一,无杂质;样品致密度高,元素分布均匀,无偏聚;所制备的样品的晶体结构均与结构因子预测的晶体结构一致。采用3 MeV Xe离子辐照样品以评估五种钙钛矿的抗辐照性能,掠入射X射线衍射测试结果表明各组分样品在离子束辐照下出现不同程度的晶格肿胀和非晶化。通过对晶胞体积肿胀率和非晶化含量的定量计算与对比,确定了五种钙钛矿的抗辐照损伤能力,发现ABO3钙钛矿的抗辐照性能与化学组分相关,且存在离子质量效应。辐照实验的分析结果表明,ABO3钙钛矿的抗辐照性能随着Goldschmidt容忍因子(t)和(µ+t)η(其中µ为八面体因子,η为原子堆积比)数值的增加而变差,随着新的容忍因子(τ)数值的增加而增强(除SrZrO3)。进一步通过第一性原理计算从ABO3钙钛矿的热力学稳定性角度对辐照实验得到的结论进行验证,结果表明ABO3钙钛矿的抗辐照性能与热力学稳定性成反比,这与另一种高放废物固化基材烧绿石氧化物的相关研究结果一致。也就是说,ABO3钙钛矿的抗辐照性能确与结构因子紧密相关,这为评估ABO3钙钛矿的抗辐照性能提供了新的思路,可凭借结构因子预测ABO3钙钛矿的抗辐照性能,或借助结构因子构造新型高性能的抗辐照钙钛矿。

Other Abstract

Perovskites are regarded as promising high-level nuclear waste candidate immobilization matrices due to their excellent physical stability, chemical stability and radiation resistance. High-level nuclear waste has ultra-high radioactive, which requires a higher irradiation stability of the immobilization matrices. How to improve and predict the radiation resistance of perovskites is of great significance. Based on the radiation effect of perovskite oxides, two research work were studied: (1) the influence of layered structure on the irradiation behavior of perovskite was systematically studied for the first time based on Ruddlesden-Popper (RP) phase (SrTiO3)nSrO (n=1, 2, 3, ∞) perovskites; (2) the correlation between radiation resistance and structural factors of perovskite oxides was explored based on ABO3 (A=Ca, Sr, Ba; B=Ti, Zr) perovskites.

The first work in this paper is to explore the influence of layered structure on the irradiation behavior of RP phase (SrTiO3)nSrO (n=1, 2, 3, ∞) perovskites. RP phase (SrTiO3)nSrO (n=1, 2, 3, ∞) perovskite samples were prepared by solid-state reaction method, and the microstructure of the materials was characterized by X-ray diffraction, laser confocal Raman spectroscopy, transmission electron microscopy and scanning electron microscopy. The result shows that the prepared samples have a single phase without impurities. (SrTiO3)nSrO (n=∞), i.e., SrTiO3 is cubic phase (lattice constant a=b=c), (SrTiO3)nSrO (n=1, 2, 3) are all tetragonal phase (lattice constant a=b≠c). The crystal plane spacing measured by transmission electron microscopy is consistent with the X-ray diffraction result, and the samples all have high crystallinity. The surface morphology of SrTiO3 and (SrTiO3)nSrO (n=1, 2, 3) are spherical and rod-shaped respectively, which are consistent with their crystal structures of cubic phase and tetragonal phase. The lattice constant c value of (SrTiO3)nSrO (n=1, 2, 3) increases linearly with the increase of n value, which is consistent with the [SrO] and [SrTiO3] orderly stacking in RP phase (SrTiO3)nSrO (n=1, 2, 3).

In order to explore the structural evolution behavior of the samples under ion beam irradiation, the 3 MeV Xe ion was used to irradiate samples. The structure of the samples before and after irradiation was characterized by grazing incidence X-ray diffraction. (SrTiO3)nSrO (n=1, 2, 3, ∞) underwent different degrees lattice swelling and amorphization under 3 MeV Xe ion irradiation at room temperature. For the same component, the relative variations of unit cell volume swelling and amorphous fraction gradually increase with the increase of ion fluence. Under the same ion fluence, the radiation resistance of (SrTiO3)nSrO (n=1, 2, 3, ∞) is enhanced with the increase of n value (i.e., decrease of the density of the SrO layer for RP phase). Under 3 MeV Xe ion irradiation at 350 ℃ and 650 ℃, SrTiO3 always maintained its original crystal structure, however, (SrTiO3)nSrO (n=1, 2, 3) gradually decomposed into SrTiO3 and SrO with the increase of temperature and ion fluence. The radiation resistance of (SrTiO3)nSrO (n=1, 2, 3, ∞) also increased with the increase of n value at high-temperature ion beam irradiation. The samples of unirradiated and irradiated at room temperature were annealed at 350 ℃ for 1 h, and the results showed that the phase transition of (SrTiO3)nSrO (n=1, 2, 3) under high temperature irradiation was the result of the synergistic effect of temperature and irradiation. In this part of the research work, the influence of the RP phase layered structure on the radiation resistance of the material at room temperature and high temperature was clarified.

Another work in this paper is to study the correlation between radiation resistance and structural factors of perovskite oxides. Five ABO3 (A=Ca, Sr, Ba; B=Ti, Zr) perovskites with different structural factors were prepared by solid-state reaction method, and the microstructure of the materials was characterized by X-ray diffraction and scanning electron microscopy. The result show that each sample has a single phase without impurities. The sample has high density, uniform element distribution, and no element agglomeration. The crystal structure of the prepared samples is consistent with the crystal structure predicted by the structural factor. In order to evaluate the radiation resistance of five perovskites, the 3 MeV Xe ion were used to irradiate samples. The grazing incidence X-ray diffraction results showed that each component sample underwent different degrees of lattice swelling and amorphization under ion beam irradiation. Through the quantitative calculation of the relative variations of unit cell volume swelling and amorphous fraction, the radiation resistance of five perovskites was determined. It is found that the radiation resistance of ABO3 perovskites is related to chemical components, that is to say, there exists ion-mass effect. The analysis results of irradiation experiments show that the radiation resistance of ABO3 perovskite deteriorates with the increase of Goldschmidt’s tolerance factor (t) and (µ+t)η (where µ is octahedral factor and η is atomic packing fraction) and decrease of new tolerance factor (τ), except SrZrO3. Furthermore, the conclusion obtained by irradiation experiments is verified by first-principles calculation from the perspective of thermodynamic stability. The result shows that the radiation resistance of ABO3 perovskites is inversely proportional to the thermodynamic stability, which is consistent with the result of pyrochlore oxide (another high-level waste immobilization matrices). In other words, the radiation resistance of ABO3 perovskites is closely related to structural factors, which provides a new idea to evaluate the radiation resistance of ABO3 perovskites. That is to say, we can predict the ability to resist radiation damage of ABO3 perovskites and construct new perovskite with high performance to resist radiation damage by structural factors.

MOST Discipline Catalogue工学 - 核科学与技术
URL查看原文
Language中文
Other Code262010_220200920630
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/537420
Collection核科学与技术学院
Affiliation
兰州大学核科学与技术学院
Recommended Citation
GB/T 7714
王梦辉. 钙钛矿氧化物的辐照效应研究:层状结构与结构因子的影响[D]. 兰州. 兰州大学,2023.
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