磷族Zintl相新化合物的合成探索与性质

发布时间：2018-06-02 18:51

本文选题：Zintl相 + 晶体结构　；参考：《山东大学》2017年博士论文

【摘要】：磷族Zintl相化合物数目众多,凭借其复杂多样的晶体结构和组分构成,在很多领域都表现出应用潜力,例如锂电、超导、巨磁阻和热电等。随着Zintl相化合物的种类日益丰富,其新颖的物理化学性质使之作为新型功能材料的潜力备增。本文通过金属助溶剂法和高温固相法合成了一系列磷族Zintl相化合物,并对其晶体结构、电子结构、磁性和热电性质进行了研究。研究内容和主要结果包括:(1)Sr14MgSb11和Eu14MgSb11的结构、磁性和热电性质用固相方法在1323 K合成了两个含Mg的锑基Zintl相化合物:Sr14MgSb11和Eu14MgSb11。两个化合物是Ca14AlSb11结构的衍生物,属于四方晶系、I41/acd空间群。Sr14MgSb11的单胞参数 a/c 是 17.5691(14)A/23.399(4)A,Eu14MgSb11 的单胞参数a/c是17.3442(11)A/22.981(3)A。电阻率与温度的关系表明,Sr14MgSb11属于本征半导体,而Eu14MgSb11属于半金属化合物。凭借低的热导率和适中的Seebeck系数,Sr14MgSb11和Eu14MgSb11具有作为热电材料的潜力。磁性测试表明,Eu14MgSb11是反铁磁性化合物,外斯温度θ为-9.49 K。电子结构计算显示,Sr14MgSb11的带隙为1.18 eV。(2)A14MgBi11(A=Ca,Sr,Eu,Yb)的结构、磁性和热电性质用固相法合成了三个Bi基14-1-11化合物A14MgBi11(A=Ca,Sr,Eu),它们都属于四方晶系、I41/acd(No.142)空间群。Ca14MgBi11、Sr14MgBi11和 Eu14MgBi11的晶胞参数 a/c 分别是 17.0470(17)/22.665(5)A,17.854(2)/23.580(6)A 和17.6660(7)/23.2446(18)A。1000 Oe场强下的磁性测试表明,Eu14MgBi11是反铁磁性化合物。电子结构计算结果显示,Ca14MgBi11是一个带隙为1.12eV的p型半导体。由于复杂的结构和较大的分子质量,A14MgBi11(A=Ca,Sr,Eu,Yb)具有低的热导率,ZT值在1073 K时分别达到0.21,0.71,0.46和0.55。随着该系列化合物的发现,14-1-11热电材料的研究范围也从Sb基化合物拓展到Bi基化合物,并且Bi化合物是一类很有前景的热电功能材料。(3)Sr14MgAs11和Eu14MgAs11的结构、磁性和光学性质用高温固相法合成了两个Zint1相化合物:Sr14MgAs11和Eu14MgAs11,这是首次报道As基含Mg的14-1-11化合物。Sr14MgAs11的单胞参数为a=16.581 A,c=22.052 A;Eu14MgAs11的单胞参数为 a=16.3046 A,c=21.857 A。两个化合物都属于四方晶系,I41/acd(No.142,Z 8)空间群。Sr14MgAs11中As4原子存在占据率为16.3%的无序,As含量的减少导致精修后的分子式为Sr14MgAs10.33。热分析表明,Eu14MgAs11在300K-973 K范围内是稳定的。磁性测试表明,当温度为7.2 K时Eu14MgAs11发生反铁磁性转变。光学吸收测试显示,Sr14MgAs11和Eu14MgAs11都是间接吸收半导体,带隙分别是2.05 eV和1.92 eV。使用Wien2K软件计算了态密度,结果显示Sr14MgAs11是p型半导体。Sr14MgAs11和Eu14MgAs11的电学和热学性质需要进一步研究,凭借良好的热稳定性和复杂的晶体结构,两个化合物有可能具有热电材料应用潜力。(4)Sr9Mg4.56Sb9的合成与晶体结构使用金属助溶剂法合成了新化合物Sr9Mg4.56Sb9,这是第一个被报道的含Mg的9-4-9化合物。Sr9Mg4.56Sb9属于正交晶系、Pnna(No.62,Z=4)空间群。单胞参数 a=13.0962(11)A,b=4.8193(4)A,c=46.259(4)A。阴离子框架是由[MgSb4]四面体与[MgSb3]平面三角形共边或者共顶点连接形成的链条,阳离子Sr2+分布在链与链的中间。Mg和Sb的多个位置都存在无序现象,凭借高密度点缺陷和复杂结构,Sr9Mg4.56Sb9可能有低的热导率和良好的热电性能。(5)Sr11Mg4As10的晶体结构和电子结构用金属Sn做助溶剂,合成了一个全新比例的Zint1相化合物Sr11Mg4As10)。该化合物属于正交晶系、Pnnm(No.58)空间群。晶胞参数a=14.542(6)A,b=22.018(10)A,c=4.4981(19)A。阴离子部分是由[MgAs4]四面体共顶点连接组成的一维链,Sr2+作为阳离子分布链中间。计算电子结构表明,Sr11Mg4As10属于半导体。(6)Ca2Si的热电性质使用电磁感应熔炼炉制备了 Ca2Si多晶样品,对其电学和热学性质进行了研究,这是该化合物的热电性能第一次被报道。电阻率随温度上升一直缓慢升高,显示出了强烈的金属性。虽然Ca2Si有较低的热导率(约1 W/m·K),但是由于其较低的Seebeck系数,最大ZT值在873 K只达到0.1左右。通过Si/Sn互掺,制备了 Ca2Si1-xSnx(0x1)系列化合物,这有可能调节载流子浓度,提高材料的热电性能。
[Abstract]:A large number of Zintl phase compounds have shown potential applications in many fields, such as lithium, superconductivity, giant magnetoresistance and thermoelectricity in many fields. With the increasing variety of Zintl phase compounds, their novel physical and chemical properties make it potential as a new functional material. A series of phosphorous Zintl phase compounds were synthesized by metal cosolvent method and high temperature solid state method, and their crystal structure, electronic structure, magnetic properties and thermoelectric properties were studied. The contents and main results include: (1) the structure of Sr14MgSb11 and Eu14MgSb11, magnetic and thermoelectric properties, two Mg containing antimony were synthesized by solid method in 1323 K Base Zintl phase compounds: two compounds of Sr14MgSb11 and Eu14MgSb11. are derivatives of Ca14AlSb11 structure and belong to the tetragonal system. The single cell parameter a/c of I41/acd space group.Sr14MgSb11 is 17.5691 (14) A/23.399 (4) A, and the a/c cell parameter of Eu14MgSb11 is 17.3442 (11) A/22.981 (3) and the relation between resistivity and temperature. Semiconductors, and Eu14MgSb11 belong to semi metal compounds. With low thermal conductivity and moderate Seebeck coefficients, Sr14MgSb11 and Eu14MgSb11 have potential as thermoelectric materials. Magnetic tests show that Eu14MgSb11 is antiferromagnetic, and the outer temperature theta is a -9.49 K. electronic structure, and the band gap of Sr14MgSb11 is 1.18 eV. (2) A14MgBi11 (2). The structure, magnetic and thermoelectric properties of A=Ca, Sr, Eu, Yb) are composed of three Bi based 14-1-11 compounds, A14MgBi11 (A=Ca, Sr, Eu), all of which belong to the tetragonal system, I41/acd (No.142) space group, respectively, 17.0470 (17) (5), 17.854 (2) 6 (6) and 17.6660 (7) (7). 18) the magnetic test under the A.1000 Oe field strength shows that Eu14MgBi11 is an antiferromagnetic compound. The results of the electronic structure calculation show that Ca14MgBi11 is a p type semiconductor with a gap of 1.12eV. Due to the complex structure and large molecular mass, the A14MgBi11 (A=Ca, Sr, Eu, Yb) has a low thermal conductivity, and the ZT values are reached and 0 respectively at the time of 1073. .55. with the discovery of this series of compounds, the research scope of 14-1-11 thermoelectric materials is also extended from Sb based compounds to Bi based compounds, and Bi compounds are a very promising thermal functional material. (3) the structure of Sr14MgAs11 and Eu14MgAs11, magnetic and optical properties have been synthesized by high temperature solid phase method for two Zint1 phase compounds: Sr14MgAs11 and Eu. 14MgAs11, this is the first report that the single cell parameter of the 14-1-11 compound containing the Mg of the As based.Sr14MgAs11 is a=16.581 A, c=22.052 A, and the single cell parameter of Eu14MgAs11 is a=16.3046 A, and the two compounds are all Quartet systems. Sr14MgAs10.33. thermal analysis of the molecular formula after refinement indicates that Eu14MgAs11 is stable within the range of 300K-973 K. The magnetic test shows that when the temperature is 7.2 K, Eu14MgAs11 has an antiferromagnetic transition. The optical absorption test shows that both Sr14MgAs11 and Eu14MgAs11 are indirect absorption semi conductors, and the band gap is 2.05 eV and 1.92 eV. uses Wien2. The K software calculates the density of States, the results show that Sr14MgAs11 is p type semiconductor.Sr14MgAs11 and Eu14MgAs11, the electrical and thermal properties need further study. With good thermal stability and complex crystal structure, the two compounds may have potential for application of thermoelectric materials. (4) the synthesis of Sr9Mg4.56Sb9 and the use of metal solubilization for crystal structure A new compound, Sr9Mg4.56Sb9, is synthesized by the agent method. This is the first reported 9-4-9 compound containing Mg,.Sr9Mg4.56Sb9 belongs to the orthogonal crystal system, Pnna (No.62, Z=4) space group. The single cell parameter a=13.0962 (11) A, b=4.8193 (4) A, c=46.259 (4) is formed by the tetrahedron with the common vertex or common vertex connection of the tetrahedron. Chain, the distribution of cationic Sr2+ in the middle of chain and chain of.Mg and Sb, there are many disordered phenomena. With high density point defect and complex structure, Sr9Mg4.56Sb9 may have low thermal conductivity and good thermoelectric properties. (5) the crystal structure and electronic structure of Sr11Mg4As10 are used as Sn as a cosolvent, and a new proportion of Zint1 phase is synthesized. Compound Sr11Mg4As10). The compound belongs to the orthogonal crystal system, the Pnnm (No.58) space group. The cell parameter a=14.542 (6) A, b=22.018 (10) A, c=4.4981 (19) A. anion part is a one-dimensional chain composed of the common vertex connection of the [MgAs4] tetrahedron, Sr2+ as a cationic distribution chain. The electronic structure shows that Sr11Mg4As10 belongs to the semiconductor. (6) heat of heat. Ca2Si polycrystalline samples were prepared by electromagnetically induced melting furnace, and their electrical and thermal properties were studied. This is the first time that the thermoelectric properties of the compound have been reported. The resistivity increases slowly with the increase of temperature, showing a strong metallic property. Although Ca2Si has a lower thermal conductivity (about 1 W/m. K), it is compared to the result of its relatively low thermal conductivity. The low Seebeck coefficient and the maximum ZT value are only about 0.1 at 873 K. A series of Ca2Si1-xSnx (0x1) compounds are prepared through the blending of Si/Sn, which may regulate the carrier concentration and improve the thermoelectric properties of the material.
【学位授予单位】：山东大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TB34

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