KR20220130451A - Relatively Heavier Cationic And Anionic Substituted Quinary Zintl Compound and Manufacturing Method Thereof - Google Patents

Abstract

By performing anionic p-type tin (Sn) doping for antimony (Sb) and cationic ytterbium (Yb) doping for calcium (Ca) in a Ca_(5-x)Yb_xAl_(2-y)In_ySb_(6-z)Sn_z system containing Al/In mixed locations, the present invention has an effect of exhibiting improved thermoelectric performance as structure complexity and conductivity increase and improved binding coefficient.

Description

Relatively Heavier Cationic And Anionic Substituted Quinary Zintl Compound and Manufacturing Method Thereof

The present invention relates to a _{five - component Jintle compound having improved thermoelectric} properties by being substituted with relatively heavy cations and _anions , and a method for preparing the same. The present invention relates to a five-component Jintle compound obtained by performing anionic p-type tin (Sn) doping for antimony (Sb) and cationic ytterbium (Yb) substitution for calcium (Ca) and a method for preparing the same.

Thermoelectric materials are evaluated as one of the most promising energy recycling technologies that can reduce global energy consumption in that they can convert wasted heat generated from various resources such as industrial plants, power plants, and automobiles into electricity.

The thermoelectric material includes Zintl phase compounds, TAGS, Half-Heusler, PbTe, and skutterudites. Among them, Zintl phase compounds are used for high-temperature thermoelectric applications due to their complex structure-based semiconductor properties and low thermal conductivity. It is evaluated as one of the best candidates for the field. Examples of the Jintle compound include A ₁₄ MSb ₁₁ (A=Ca, Yb; M=Mn, Al), A ₅ Al ₂ Sb ₆ (A=Ca, Yb), A ₁₁ Pn ₁₀ (A=Ca, Yb; Pn) =Sb, Bi, Sn) and A ₂ CdSb ₂ (A=Ca, Yb, Eu).

According to a recent study, the carrier of the Ca ₅ Al _{2- x} In _x Sb ₆ system, which is a synthal compound, increases its mobility as aluminum (Al) is replaced with indium (In); It has been reported that in the Ca ₅ Al _{1.9- x} In _x Zn _0.1 Sb ₆ system, when the Al/In mixed position is doped with zinc (Zn), the concentration of carriers increases and the electrical conductivity is improved. In particular, since the zinc doping improves phonon scattering of the system, the lattice thermal conductivity of the system is lowered, and as a result, the thermoelectric performance (ZT) is improved. Therefore, it is expected that a new material with improved thermoelectric performance can be developed by improving the conventional Jintle compound using various elements that can be doped.

The patents and references mentioned in this specification are hereby incorporated by reference to the same extent as if each publication were individually and expressly specified by reference.

Y. Pei, X. Shi, A. LaLonde, H. Wang, L. Chen, G. J. Snyder, Nature 2011, 473, 66-69. A. Kumar, P. A. Vermeulen, B. J. Kooi, J. Rao, L. van Eijck, S. Schwarzmuller, O. Oeckler, G. R. Blake, Inorg. Chem. 2017, 56, 15091-15100. W. G. Zeier, J. Schmitt, G. Hautier, U. Aydemir, Z. M. Gibbs, C. Felser, G. J. Snyder, Nature Rev. Mater. 2016, 1, 16032. C. Han, G. Tan, T. Varghese, M. G. Kanatzidis, Y. Zhang, ACS Energy Lett. 2018, 3, 818-822. W. Li, J. Wang, Y. Xie, J. L. Gray, J. J. Heremans, H. B. Kang, B. Poudel, S. T. Huxtable, S. Priya, Chem. Mater. 2019, 31, 862-872. J. Lee, K. Ahn, K. Kim, H. Jo, J. S. Yoon, D. Moon, W. H. Shin, K. M. Ok, T.-S. You, Cryst. Growth Des. 2019, 19, 3498-3508. G. Nam, E. Jang, H. Jo, M.- K. Han, S.-J. Kim, K. M. Ok, T.-S. You, Materials 2016, 9, 553. E. S. Toberer, C. A. Cox, S. R. Brown, T. Ikeda, A. F. May, S. M. Kauzlarich, Adv. Funct. Mater. 2008, 18, 2795-2800. G. Nam, W. Choi, H. Jo, K. M. Ok, K. Ahn, T. -S. You, Chem. Mater. 2017, 29, 1384-1395 G. Nam, W. Choi, J. Lee, S.-J. Lim, H. Jo, K. M. Ok, K. Ahn, T.-S. You, Inorg. Chem. 2017, 56, 7099-7110. Y. Liang, R. Cardoso-Gil, W. Schnelle, J. Zhao, Y. Grin, Solid State Sci. 2013, 18, 127-130. K. Kim, J. Lee, S. Shin, H. Jo, D. Moon, K. M. Ok, T.-S. You, Cryst. Growth Des. 2020, 20, 746-754. K. Kim, H. Jo, K. M. Ok, T.-S. You, Bull. Korean Chem. Soc. 2020, 41, 245-247. A. Zevalkink, J. Swallow, S. Ohno, U. Aydemir, S. Bux, G. J. Snyder, Dalton Trans. 2014, 43, 15872-15878. G.-T. Bae, Bull. Korean Chem. Soc. 2019, 40, 780-786. E. S. Toberer, A. Zevalkink, N. Crisosto, J. Snyder, Adv. Funct. Mater. 2010, 20, 4375-4380. A. Zevalkink, G. S. Pomrehn, S. Johnson, J. Swallow, Z. M. Gibbs, G. J. Snyder, Chem. Mater. 2012, 24, 2091-2098. S. J. Lim, G. Nam, S. Shin, K. Ahn, Y. Lee, T.-S. You, Inorg. Chem. 2019, 58, 5827-5836. J. Lee, S. Shin, H. Jo, W. H. Shin, D. Moon, K. M. Ok, T.-S. You, Inorg. Chem. 2020, 59, 13572-13582. J. Emsley, The Elements; Oxford University Press: New York, 1989. J. Lee, H. Sa, H. Jo, D. Moon, K. M. Ok, T.-S. You, Cryst. Growth Des. 2020, 20, 4503-4511.

The present invention is to develop a new material having improved thermoelectric performance by improving the conventional Jintle compound using various elements that can be doped, Ca _{5- x} Yb _x Al _{2- y} In _y Provided are a Jintle compound in which anionic p-type tin (Sn) doping for antimony (Sb) and cationic ytterbium (Yb) substitution for calcium (Ca) is performed in a Sb _{6- z} Sn _z system, and a method for preparing the same but it has a purpose.

Other objects and technical features of the present invention are set forth more specifically by the following detailed description of the invention, claims and drawings.

The present invention relates to a Jintle compound comprising an Al/In mixed atomic position occupied by a mixture of aluminum (aluminum, Al) atoms and the indium (In) atoms,

the following formula;

[Formula]

x

3.98; 0.27

y

0.52; 0

z

0.56)Ca _{5- x} Yb _x Al _{2- y} In _y Sb _{6- z} Sn _z (0

x

3.98; 0.27

y

0.52; 0

z

0.56)

(Wherein, Ca is calcium; Yb is ytterbium; Al is aluminum; In is indium; Sb is antimony; Sn is tin.);

The Jintle compound is Ca _1.02 Yb _3.98 Al _1.48 In _0.52 Sb ₆ or Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 and orthorhombic Ca ₅ Ga ₂ Sb ₆ -type (space group Pbam , Pearson code oP 26, Z = 2) It is characterized by having a structure.

The Jintle compound is synthesized by an arc-melting method and is characterized in that it is prepared by post-heat treatment at a temperature of 1062 to 1082 K for 5 to 9 days.

_The present invention provides _anionic p _- type _tin ( _Sn ) _doping and _calcium ( _Sn ) _doping and calcium ( Since the cationic ytterbium (Yb) substitution for Ca) is performed, the complexity and electrical conductivity of the structure are increased, and the Seebeck coefficient is improved, so there is an effect of showing improved thermoelectric performance.

)과 양이온 원자위치로 구성된 단위 셀(unit cell)을 보여주며, 패널(c), (d) 및 (e)는 Ca_1.02Yb_3.98Al_1.48In_0.52Sb₆의 세 가지 Ca/Yb 혼합 원자 위치를 보여준다.
도 4는 본 발명의 표제 화합물에 대한 DOS 분석 결과 및 밴드 구조 분석 결과를 보여준다. 패널(a) Ca₅Al_1.5In_0.5Sb₆에 대한 DOS 분석 결과 및 밴드 구조 분석 결과를 보여주며, 패널(b)는 Ca₅Al_1.5In_0.5Sb_5.5Sn_0.5에 대한 DOS 분석 결과 및 밴드 구조 분석 결과를 보여준다. E _F는 점선으로 표시하였으며, TDOS는 검정색의 굵은 선으로 표시하였으며 Ca PDOS는 회색 영역으로 표시하였으며, Sb PDOS는 노란색 영역으로 표시하였으며, Sn PDOS는 핑크색 영역으로 표시하였으며, Al PDOS는 보라색 역역으로 표시하였으며, In PDOS는 녹색 영역으로 표시하였다.1 shows the results of PXRD analysis of the title compound of the present invention. Panel (a) shows the results for Ca _1.02 Yb _3.98 Al _1.48 In _0.52 Sb ₆ , and panel (b) shows the results for Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 .
2 shows the results of the phase transition according to the post-heat treatment of the title compound Ca _1.02 Yb _3.98 Al _1.48 In _0.52 Sb ₆ of the present invention.
3 shows the crystal structure of the title compound of the present invention. Panel (a) shows the structure of the anionic [(Al/In) ₂ (Sb/Sn) ₈ ] dimer of Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 , and panel (b) shows the one-dimensional (1D) anion chain (

) and cation atomic positions are shown, and panels (c), (d) and (e) show three Ca/Yb mixed atomic positions: Ca _1.02 Yb _3.98 Al _1.48 In _0.52 Sb ₆ . show
4 shows the results of DOS analysis and band structure analysis for the title compound of the present invention. Panel (a) shows DOS analysis results and band structure analysis for Ca ₅ Al _1.5 In _0.5 Sb ₆ , and panel (b) shows DOS analysis results and band structure analysis for Ca ₅ Al _1.5 In _0.5 Sb _5.5 Sn _0.5 show the results E _F is indicated by a dotted line, TDOS is indicated by a thick black line, Ca PDOS is indicated by a gray region, Sb PDOS is indicated by a yellow region, Sn PDOS is indicated by a pink region, and Al PDOS is indicated by a purple region. is indicated, and In PDOS is indicated by a green area.

The present invention relates to a Jintle compound comprising an Al/In mixed atomic position occupied by a mixture of aluminum (Aluminum, Al) atoms and the indium (In) atoms,

the following formula;

[Formula]

x

3.98; 0.27

y

0.52; 0

z

0.56)Ca _{5- x} Yb _x Al _{2- y} In _y Sb _{6- z} Sn _z (0

x

3.98; 0.27

y

0.52; 0

z

0.56)

(Wherein, Ca is calcium; Yb is ytterbium; Al is aluminum; In is indium; Sb is antimony; Sn is tin.);

It provides a Zintle compound represented by .

The Jintle compound of the present invention is a five-component Jintle compound and is a five-component derivative of the four-component compound Ca ₅ Al _2-x In _x Sb ₆ series.

The Jintle compound is characterized in that Ca _1.02 Yb _3.98 Al _1.48 In _0.52 Sb ₆ or Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 , and the Ca _1.02 Yb _3.98 Al _1.48 In _0.52 Sb ₆ is the cationic atom Ca is cationic. The derivative is substituted with the atom Yb, and the Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 is a derivative in which the anionic atom Sb is doped with the anionic atom p-type Sn.

The Jintle compound is prepared by post-heating the compound synthesized using the arc-dissolution method at a temperature of 1062 to 1082 K for 5 to 9 days.

The preparation method for Ca _1.02 Yb _3.98 Al _1.48 In _0.52 Sb ₆ among the Jintle compounds is to react Ca, Yb, Al, In, Sb with Ca:Yb:Al:In:Sb=1:4:1.5:0.5:6. A first step of synthesizing the five-component Jintle compound by mixing in a ratio and then melting and reacting in an arc melting furnace; a second step of preparing a second five-component Jintle compound with improved homogeneity by repeating remelting and cooling six or more times for the synthesized five-component Jintle compound; and a third step of producing Ca _1.02 Yb _3.98 Al _1.48 In _0.52 Sb ₆ , which is a five-component Jintle compound, by post-heating the second five-component Jintle compound at a temperature of 1062 to 1082 K for 5 to 9 days.

The Ca _1.02 Yb _3.98 Al _1.48 In _0.52 Sb ₆ has a Ba ₅ Al ₂ Bi ₆ type crystal phase at the time of particularly arc-melting method, but after the post-heat treatment, Ca ₅ Ga ₂ Sb ₆ type (space group Pbam , Pearson Code oP 26, Z = 2) has a structure.

The detailed structure of the Ca _1.02 Yb _3.98 Al _1.48 In _0.52 Sb ₆ crystal phase is an Al atom and an In atom occupying a mixed atomic position of Al/In, an Sb atom occupying the Sb1 atomic position, an Sb atom occupying an Sb2 atomic position, and a one-dimensional anion chain ([(Al/In) ₂ (Sb1) ₂ (Sb2) ₂ (Sb3) ₂ ]) consisting of Sb atoms occupying the Sb3 atomic positions runs along the c-axis and forms the Ca1/Yb1 mixed atomic positions. A cation atom composed of a Ca atom and Yb atom mixedly occupying a Ca2/Yb2 mixed atomic position, a Ca atom and a Yb atom mixed and occupied a Ca3/Yb3 mixed atomic position, and a Ca atom and a Yb atom mixed and occupying the Ca3/Yb3 mixed atomic position is between the one-dimensional anion chains. It is characterized in that it fills the voids of

Therefore, the five-component Jintle compound of the present invention Ca _1.02 Yb _3.98 Al _1.48 In _0.52 Sb ₆ is the Ca ₅ Al _2-x In _x Sb ₆ series, which is a four-component compound, Ca (atomic weight 40.08, electronegativity 1.0) is Yb ( Since it is doped with an atomic weight of 173.04 and electronegativity 1.1), the effective mass value is increased, the valence electrical conductivity is increased, and the crystal structure is advanced, so the thermoelectric performance is improved.

The method for preparing Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 of the Jintle compound is a method for preparing reactants Ca, Al, In, and Sn in a ratio of Ca:Al:In:Sb:Sn=5:1.5:0.5:5.3:0.7. A first step of synthesizing a five-component Jintle compound by mixing and then melting and reacting in an arc melting furnace; a second step of preparing a second five-component Jintle compound with improved homogeneity by repeating remelting and cooling six or more times for the synthesized five-component Jintle compound; and a third step of producing Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 , which is a five-component Jintle compound, by post-heating the second five-component Jintle compound at a temperature of 1062 to 1082 K for 5 to 9 days.

The Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 has a Ca ₅ Ga ₂ Sb ₆ type (space group Pbam , Pearson code oP 26, Z = 2) structure in both the crystalline phase synthesized by arc-melting and the crystalline phase prepared after post-heat treatment. has the characteristics of

The detailed structure of the Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 crystal phase is an Al atom and In atom occupying the Al/In mixed atomic position, an Sb atom occupying the Sb1 atomic position, and the Sb2/Sn mixed atomic position. A one-dimensional anion chain ([(Al/In) ₂ (Sb1) ₂ (Sb2/Sn) ₂ (Sb3) ₂ ]) consisting of Sb and Sn atoms, and Sb atoms occupying the Sb3 atomic positions, is formed along the c-axis. Subsequently, it is characterized in that a cation atom composed of a Ca atom occupying a Ca1 atomic position, a Ca atom occupying a Ca2 atomic position, and a Ca atom occupying a Ca3 atomic position fills the void between the one-dimensional anion chains.

Therefore, the five-component Jintle compound of the present invention Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 has improved electrical conductivity because Sb is doped with p-type Sn compared to the Ca ₅ Al _2-x In _x Sb ₆ series, which is a four-component compound. As the effective mass value increases, the Seebeck coefficient is improved, the thermal conductivity is lowered, and the crystalline structure is advanced, so the thermoelectric performance is improved. The above result is considered to be because the Sb was doped with p-type Sn and the Sn p-orbital contributed to the electronic structure of the compound.

Hereinafter, the present invention will be described in detail through examples.

Example

1. Experimental method

1) Synthesis of compounds

All samples were prepared in a glove box filled with argon (Ar) gas at an O ₂ and H ₂ O content of 0.1 ppm or less or under vacuum. The reactants Ca(shot, 99.5%), Yb(ingot, 99.9%), Al(shot, 99.9%), In(shot, 99.99%), Sb(shot, 99.999%), and Sn(shot, 99.8%) are All were purchased from Alfa Aesar.

The tanned surfaces of Ca and Yb ingots were cleaned by scraping with a scalpel or metal brush before use. The two five-component title compounds were synthesized using arc-melting method. Ca _1.02 Yb _3.98 Al _1.48 In _0.52 Sb ₆ silver reactant was mixed in a ratio of Ca:Yb:Al:In:Sb=1:4:1.5:0.5:6, and Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 was synthesized. The reactants were synthesized by mixing in a ratio of Ca:Al:In:Sb:Sn=5:1.5:0.5:5.3:0.7.

x

5), CaYb₄Al₂Sb_{6- x} Ge _x (x=0.2, 0.5, 0.7), 및 Ca_{5- x} Yb _x Al_{2- y} In _y Sb₆(3.07(1)

x

4.88(2); 0.16(2)

y

2.00) 시스템이 있다. 도 2의 패널(a) 및 (b)는 상기 특정한 상전이에 대한 PXRD 패턴을 보여준다. To ensure the homogeneity of the compound, it was redissolved at least 6 times and annealed (post-heat treatment) at 1072 K for one week after the initial synthesis. As a result, it was confirmed that the title compound containing the Ca/Yb mixture, Ca _1.02 Yb _3.98 Al _1.48 In _0.52 Sb ₆ , exhibited a solid phase transition from the original Ba ₅ Al ₂ Bi ₆ form to the Ca ₅ Ga ₂ Sb ₆ form. This type of phase transition has been previously observed in four-component and five-component analogs, for example Ca ₅ - _x Yb _x Al ₂ Sb ₆ (1

x

5), CaYb ₄ Al ₂ Sb _{6- x} Ge _x ( x =0.2, 0.5, 0.7), and Ca _{5- x} Yb _x Al _{2- y} In _y Sb ₆ (3.07(1))

x

4.88(2); 0.16(2)

y

2.00) system. Panels (a) and (b) of FIG. 2 show PXRD patterns for the specific phase transition.

2) Determination of crystal structure

2θ

75° 범위에서 0.05°로 설정되었으며 각 샘플 당 총 노출 시간은 1 시간이었다. 상기 두 가지 표제 화합물의 상(phase) 순도는 수집된 PXRD 패턴과 두 가지 SXRD 개선(refinement) 결과를 이용하여 만든 시뮬레이션 패턴을 비교하는 방법으로 확인하였다. Powder X-Ray Diffraction (PXRD) and Single-crystal X-ray Diffraction (SXRD) experiments were performed on the two title compounds. The PXRD patterns were obtained at room temperature using a Bruker D8 diffractometer equipped with an area detector and monochromatic Cu Kα1 radiation. Acquisition stage size is 15°

2θ

The 75° range was set at 0.05° and the total exposure time for each sample was 1 hour. The phase purity of the two title compounds was confirmed by comparing the collected PXRD patterns and simulation patterns made using the two SXRD refinement results.

As a result of the analysis, Ca _1.02 Yb _3.98 Al _1.48 In _0.52 Sb ₆ and Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 synthesized by arc melting method were adopted as Ba ₅ Al ₂ Bi ₆ type and Ca ₅ Ga ₂ Sb ₆ type, respectively. However, as a result of further post-heat treatment (annealing), Ca _1.02 Yb _3.98 Al _1.48 In _0.52 Sb ₆ containing Ca/Yb mixed atoms showed a phase transition from Ba ₅ Al ₂ Bi ₆ type to Ca ₅ Ga ₂ Sb ₆ type. was confirmed (panels (a) and (b) in FIG. 3).

SXRD data for the two title compounds were obtained from synchrotron radiation (λ) from the Rayonix MX225HS detector of BL2D SMC using a silicon(111) double crystal monochromator (DCM) at Pohang accelerator laboratory (PAL). =0.61000 Å) at room temperature. Data collection (detector distance 66mm, omega scan, Δω=3°, exposure time 0.6sec/frame) was performed using the PAL BL2D-SMDC program, and data integration and reduction was performed using the HKL3000sm (Ver. 716.7). did.

Unit cell parameter improvement was performed using the SAINT program, and SADABS was used to perform semi-empirical absorption corrections based on equivalence. Through the above process, the total reflection set for the two five-component title compounds was confirmed to have an orthorhombic space group Pbam , and the overall isomorphic crystal structure was adjusted to Ca ₅ Ga ₂ Sb ₆ type.

The detailed crystal structure was determined by the direct method and subdivided to converge to the full matrix least squares method in F ² . Improved parameters include scale factor, atomic position including anisotropic displacement parameters (ADP), extinction coefficient and Ca/Yb mixed atomic position, Al/In mixed atomic position and the occupancy factor of Sb/Sn mixed atomic positions. Important crystallographic data, atomic positions including ADP, and selected interatomic distances are listed in Tables 1, 2 and 3.

The SXRD data can be found at the Cambridge Data Center (www.ccdc.cam.ac.uk/data_request/cif), and accession numbers CCDC-2053273 (Ca _1.02 Yb _3.98 Al _1.46 In _0.52 Sb ₆ ) and CCDC-2053272 (Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 ).

3) Calculation of electronic structure

To understand the electron transport properties of p-type Sn doping for Sb in Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 and the effect of p-type Sn doping on Sb2 atomic positions, atomic sphere approximation (ASA) ) using a tight-binding linear muffin-tin orbital (TB-LMTO) method for a series of hypothetical models with an ideal configuration of Ca ₅ Al _1.5 In _0.5 Sb _5.5 Sn _0.5 Theoretical calculations were performed.

In order to apply the specific chemical composition, alternating atomic arrangement was allowed in the expanded unit cell by lowering the model symmetry from the improved Pbam to the subgroup Pm and doubling the size of the unit cell along the c-axis direction. The basic lattice parameters and atomic coordinates were extracted from the SXRD improvement results of Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 . For comparison, a series of calculations were performed for the four-component title compound (Ca ₅ Al _1.5 In _0.5 Sb ₆ ) not doped with p-type Sn.

All relativistic effects except spin-orbit coupling were considered using scalar relativistic approximations. In the ASA method, the space was filled with overlapping Wigner-Seitz (WS) atomic spheres. The symmetry of the potentials inside each WS sphere was considered spherical and a combined correction was used to account for overlap. The radius of the WS sphere was set so that the superposition dislocation was the best approximation to the maximum dislocation and was determined by an automated procedure. The error in kinetic energy introduced by the combined correction is proportional to the fourth power of the relative WS sphere overlap. Therefore, it is preferable that the overlap of the WS atomic spheres is not too large.

The radius of the WS sphere used in the present invention is as follows: Ca ₅ Al _1.5 In _0.5 Sb _5.5 Sn _0.5 Ca=2.14 to 2.21 Å, Al=1.57 Å, In=1.61 Å, Sb=1.70 to 1.76 Å, and Sn=1.72 to 1.76 Å; For Ca ₅ Al _1.5 In _0.5 Sb ₆ , Ca=2.14 to 2.21 Å, Al=1.57 Å, In=1.61 Å, and Sb=1.70 to 1.76 Å.

The orbitals for each element were set as follows: 4 s orbitals, 4 p orbitals and 3 d orbitals for Ca; for Al, 6 s orbitals, 6 p orbitals, 3 s orbitals, 3 p orbitals, and 3 d orbitals; 5 s orbitals, 5 p orbitals, 5 d orbitals, and 4 f orbitals for In; 5 s orbitals, 5 p orbitals, 5 d orbitals, and 4 f orbitals for Sb; For Sn, 5 s orbitals, 5 p orbitals, 5 d orbitals, and 4 f orbitals.

wdin downfolding) 방법으로 처리되었다. k-공간 통합은 사면체 방법으로 수행되었으며 일관된 전하밀도는 Brillouin 영역에서 320개의 더는 단순화할 수 없는 k-포인트를 사용하여 얻었다.4 p orbital of Ca, 3 d orbital of Al; 5 d and 4 f orbitals of In; 5 d and 4 f orbitals of Sb; and 5 d , and 4 f orbitals of Sn are rhodin downfolding (L

wdin downfolding) method. The k -space integration was performed with the tetrahedral method and consistent charge densities were obtained using 320 non-simplified k -points in the Brillouin region.

4) Energy dispersive X-ray spectroscopy

Elemental analysis was performed by energy-dispersive X-ray spectroscopy (EDS) mounted on a ULTRA Plus filed-emission scanning electron microscope system, with an accelerating voltage of 30 kV was applied.

After selecting several single crystals from the Sn-doped reactant batch, the single crystals were carefully mounted around the perimeter of an aluminum puck using double-sided conductive carbon tape in an Ar-filled glove box.

As a result of EDS analysis, it is confirmed that the result of Ca _5.08 Al _1.48 In _0.24 Sb _5.67 Sn _0.34 is similar to the SXRD improvement result of Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 .

2. Experimental results and discussion

Through the arc melting and post-heat treatment (annealing) method of the present invention, two five-component compound-like compounds, Ca _1.02 Yb _3.98 Al _1.48 In _0.52 Sb ₆ and Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 , were successfully synthesized. PXRD and SXRD analysis was performed on the crystal structure. Panels (a) and (b) of FIG. 1 show the results of comparing the PXRD pattern and the simulation pattern of the title compound of the present invention.

The title compound is considered to belong to the five-component solid solution Ca _{5- x} Yb _x Al _{2- y} In _y Sb _{6- z} Sn _z system. Accordingly, the title compound is a five-component derivative of the Ca ₅ Al _{2- x} In _x Sb ₆ series of four-component compounds, specifically, a derivative in which Ca is substituted with cationic Yb (Ca _1.02 Yb _3.98 Al _1.48 In _0.52 Sb ₆ ) and Sb is a p-type Sn doped derivative (Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 )

is considered to be

To improve the density and crystallinity of the two title compounds (Ca _1.02 Yb _3.98 Al _1.48 In _0.52 Sb ₆ and Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 ), post-heat treatment (annealing) process for one week after arc melting synthesis was applied.

x

5), CaYb₄Al₂Sb_{6- x} Ge _x (x=0.2, 0.5, 0.7), 및 Ca_{5- x} Yb _x Al_{2- y} In _y Sb₆(3.07

x

4.88; 0.16

y

2.00)시스템이 있다.Ca _1.02 Yb _3.98 Al _1.48 In _0.52 Sb ₆ of the present invention shows a phase transition between solid phase single crystals by post-heat treatment. The above results show that among compounds containing a Ca/Yb mixed atom, Yb-rich compounds, that is, A ₅ M ₂ Pn ₆ (A=alkali metal, alkaline-earth metals, rare-earth metals; M=Al, Ga, In; Pn) =pnictogens) is known to occur only in the system, for example, Ca _{5- x} Yb _x Al ₂ Sb ₆ (1

x

5), CaYb ₄ Al ₂ Sb _{6- x} Ge _x ( x =0.2, 0.5, 0.7), and Ca _{5- x} Yb _x Al _{2- y} In _y Sb ₆ (3.07

x

4.88; 0.16

y

2.00) system.

Therefore, it is determined that both of the two isomorphic title compounds are orthorhombic Ca ₅ Ga ₂ Sb ₆ -type (space group Pbam , Pearson code oP 26, Z = 2) having seven crystallographically independent atomic positions, and the atomic positions are 3 cation atom positions, 1 Al/In mixed atomic position and 3 Sb atomic positions or Sb/Sn mixed atomic positions. Detailed SXRD improvement results are shown in Tables 1, 2 and 3C

Additionally, as a result of confirming the chemical composition through EDS analysis of Ca _5.08 Al _1.48 In _0.24 Sb _5.67 Sn _0.34 , which is a conventional Sn doped compound, it was confirmed that it was in good agreement with the SXRD improvement result of Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 .

)과 상기 1차원 음이온 사슬 사이의 공간을 채우는 세 가지 유형의 양이온 위치로 설명된다. 특히 상기 1차원 음이온 사슬은 두 개의 이웃한 [(Al/In)₂(Sb/Sn)₄] 이량체가 네 개의 꼭지점 Sb3 원자들을 공유하여 구성되는 것으로 설명되며 상기 1차원 음이온 사슬은 Sb1 원자를 통해 연결된 두 개의 인접한 사면체[(Al/In)(Sb/Sn)₄] 단위로도 설명된다. 더욱이, 세 개의 양이온 원자 위치는 여섯 개 또는 일곱 개의 Sb 원자 위치 또는 Sb/Sn 혼합 원자 위치로 둘러싸여 있다. Ca1/Yb1 혼합 원자 위치와 Ca3/Yb3 혼합 원자 위치는 각각 약간 왜곡된 팔면체의 중심에 위치하는 반면 Ca2/Yb2 혼합 원자 위치는 두 모서리로 덮인 사각형 피라미드의 중앙에 위치한다(도 3의 패널(c), (d), 및 (e) 참조). 흥미롭게도 두 개의 6 배위 양이온 원자 위치 사이에 존재하는 Ca3/Yb3 혼합 원자 위치는 중앙 원자 위치와 주변 Sb 원자 위치 또는 Sb/Sn 혼합 원자 위치 사이의 원자간 거리를 기반으로 Ca1/Yb1 혼합 원자 위치에 대한 대칭적인 팔면체 기하학을 가지고 있다. 또한 상기 7-배위 Ca2/Yb2 혼합 원자 위치는 다른 세 개의 양이온 원자 위치 중 가장 큰 위치 부피를 가지는 것으로 확인된다. 따라서 Ca_1.02Yb_3.98Al_1.48In_0.52Sb₆에서 관찰되는 Ca 및 Yb의 위치 선호도는 상대적으로 작은 크기의 Ca의 경우 Ca3/Yb3 혼합 원자 위치에서 가장 큰 점유를 보여주며 상대적으로 더 큰 크기의 Yb의 경우 Ca2/Yb2 혼합 원자 위치에서 가장 큰 점유를 보여준다. 상기 결과는 각 원소의 크기 인자 기준(size-factor criterion)에 의해 설명된다. Ca와 Yb의 공유반경은 각각 r(Ca²⁺)=1.06 Å, 및 r(Yb²⁺)=1.13 Å이다. 3 shows the isoform crystal structures of two title compounds of the present invention. The overall structure consists of an infinite one-dimensional (1D) anion chain running along the c-axis direction (

) and the three types of cation positions that fill the space between the one-dimensional anion chains. In particular, the one-dimensional anion chain is described as being composed of two neighboring [(Al/In) ₂ (Sb/Sn) ₄ ] dimers sharing four vertex Sb3 atoms, and the one-dimensional anion chain is formed through an Sb1 atom It is also described as two adjacent tetrahedral [(Al/In)(Sb/Sn) ₄ ] units connected. Moreover, three cation atomic positions are surrounded by six or seven Sb atomic positions or mixed Sb/Sn atomic positions. The Ca1/Yb1 mixed atomic position and the Ca3/Yb3 mixed atomic position are located at the center of the slightly distorted octahedron, respectively, while the Ca2/Yb2 mixed atomic position is located at the center of a quadrangular pyramid covered with two corners (Fig. 3, panel (c)). ), (d), and (e)). Interestingly, the Ca3/Yb3 mixed atomic positions existing between the two 6-coordinated cation atomic positions are located at the Ca1/Yb1 mixed atomic positions based on the interatomic distance between the central and peripheral Sb atomic positions or the Sb/Sn mixed atomic positions. It has a symmetrical octahedral geometry. In addition, it is confirmed that the 7-coordinated Ca2/Yb2 mixed atomic position has the largest position volume among the other three cation atom positions. Therefore, the positional preferences of Ca and Yb observed in Ca _1.02 Yb _3.98 Al _1.48 In _0.52 Sb ₆ show the largest occupancy at the Ca3/Yb3 mixed atomic position for Ca of relatively small size, and that of Yb of relatively larger size. The case shows the largest occupancy at the Ca2/Yb2 mixed atomic position. The result is explained by the size-factor criterion of each element. The covalent radii of Ca and Yb are r (Ca ²⁺ )=1.06 Å, and r (Yb ²⁺ )=1.13 Å, respectively.

In contrast, in Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 , the position preference of anionic Sn to the Sb2 atomic position is not explained by the size-factor criterion, because the anionic elements Sb and Sn It is thought that this is because they have very similar covalent radii ( r (Sb) = 1.41 Å and r (Sn) = 1.40 Å). Thus, the negative ion position preference is described by the electronic-factor criterion rather than the size factor criterion. The negative ion position preference will be described in detail in the electronic calculation section below.

The potential effect of p-type Sn doping on the electrical transport properties of Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 of the present invention and the position of Sn relative to the three Sb atomic positions explainable by the electron factor criterion To confirm the preference, a virtual structure model, Ca ₅ Al _1.5 In _0.5 Sb _5.5 Sn _0.5 was designed and a series of theoretical calculations were performed using the TB-LMTO-ASA method. Structural information of the virtual structure model, Ca ₅ Al _1.5 In _0.5 Sb _5.5 Sn _0.5 is shown in Table 4 below.

Chemical formula Ca ₅ Al _1.5 In _0.5 Sb _5.5 Sn _0.5 space group Pm (No.6) Unit cell dimensions (Å) a = 14.1030; b = 8.9500; c = 12.0960 Volume (Å ³ ) 1526.78 Atomic coordinates Atom Wyckoff site x y z Ca1 2 c 0.2479 0.2500 0.3423 Ca2 2 c 0.7479 0.2500 0.6577 Ca3 2 c 0.7521 0.7500 0.1577 Ca4 2 c 0.2521 0.7500 0.8423 Ca5 2 c 0.0124 0.2500 0.5746 Ca6 2 c 0.5124 0.2500 0.4254 Ca7 2 c 0.9876 0.7500 0.9254 Ca8 2 c 0.4876 0.7500 0.0746 Ca9 2 c 0.0000 0.2500 0.2500 Ca10 2 c 0.5000 0.2500 0.7500 Sb1 1 a 0.5990 0.0000 0.2251 Sb2 1 b 0.0990 0.5000 0.7749 Sb3 1 a 0.9010 0.0000 0.7251 Sb4 1 b 0.4010 0.5000 0.2749 Sb5 1 a 0.4010 0.0000 0.2749 Sb6 1 b 0.9010 0.5000 0.7251 Sb7 1 a 0.0990 0.0000 0.7749 Sb8 1 b 0.5990 0.5000 0.2251 Sn1 1 a 0.9057 0.0000 0.0939 Sb9 1 b 0.4057 0.5000 0.9061 Sn2 1 a 0.5943 0.0000 0.5939 Sb10 1 b 0.0943 0.5000 0.4061 Sb11 1 a 0.0943 0.0000 0.4061 Sb12 1 b 0.5943 0.5000 0.5939 Sb13 1 a 0.4057 0.0000 0.9061 Sb14 1 b 0.9057 0.5000 0.0939 Sb15 2 c 0.3214 0.2500 0.5896 Sb16 2 c 0.8214 0.2500 0.4104 Sb17 2 c 0.6786 0.7500 0.9104 Sb18 2 c 0.1786 0.7500 0.0896 In1 1 a 0.7861 0.0000 0.9175 In2 1 b 0.2861 0.5000 0.0825 Al1 1 a 0.7139 0.0000 0.4175 Al2 1 b 0.2139 0.5000 0.5825 Al3 1 a 0.2139 0.0000 0.5825 Al4 1 b 0.7139 0.5000 0.4175 Al5 1 a 0.2861 0.0000 0.0826 Al6 1 b 0.7861 0.5000 0.9174

In addition, the DOS curve and band structure of Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 of the present invention were analyzed and compared with the results of Ca ₅ Al _1.5 In _0.5 Sb ₆ , a four-component parent compound undoped with Sn.

The results are summarized as follows.

First, the total DOS (TDOS) and partial DOS (PDOS) curves of the two compounds are judged to show overall orbital mixing over the entire energy range (see panels (a) and (b) of FIG. 4 ). In particular, in the case of the DOS curve of Ca ₅ Al _1.5 In _0.5 Sb _5.5 Sn _0.5 , the region below the Fermi level ( EF ₎ corresponding to a low energy between about -6.5 and -4.7 eV is mostly the s-orbital state of anion atoms. is found to contain In contrast, the region from -4.3 eV to _EF is found to contain the p-orbital state of these atoms with some contribution of Ca d-orbitals. Interestingly, when the valence electron count of Ca ₅ Al _1.5 In _0.5 Sb _5.5 Sn _0.5 in _EF corresponds to 45.5 VEC, the TDOS value is the valence electron count of Ca ₅ Al _1.5 In _0.5 Sb ₆ . When it corresponds to 46.0 VEC, it is confirmed that the TDOS value is slightly increased, which is determined to be due to p-type Sn doping (refer to panel (b) of FIG. 4 ). The increase in the TDOS value as described above leads to an improvement in the electrical conductivity of the p-type Sn-doped title compound.

Second, it is confirmed that the largest contribution of the newly added Sn p-orbital state is mostly concentrated in the region between -0.5 _eV and EF . Therefore, the TDOS and PDOS curves of the region are greatly improved, confirming that the band extrema at the Γ, Х and U points increases, and the region between the Γ and Z points and Γ and Х points due to p-type Sn doping. shows that the band structure is doubly degraded (see panel (b) of FIG. 4 ). Therefore, the increase in the band limit of Ca ₅ Al _1.5 In _0.5 Sb _5.5 Sn _0.5 and the degradation of the band structure mean an increase in effective mass, which leads to improvement of the Seebeck coefficient. This result is supported by the results of the conventional Ge-doped pentacomponent analog CaYb ₄ Al ₂ Sb _{6- x} Ge _x ( x =0.2, 0.5, 0.7) system. Additionally, atomic disordering due to the compound containing Ca/Yb mixed atoms and the compound containing Sb/Sn mixed atoms was found to affect phonon scattering, which in turn resulted in thermal conductivity. leads to a decrease in

Third, in order to understand the position preference of anionic Sn for the Sb2 atomic position based on the electron factor criterion, the QVAL of each atomic position for the four-component parent compound, Ca ₅ Al _1.5 In _0.5 Sb ₆ , was analyzed. As described above, Sb and Sn have very similar atomic sizes. Therefore, the positional preference associated with Sb and Sn should be explained by the electronic factor criterion rather than the size factor criterion. The electron factor criterion is based on the QVAL of a specific atomic site and the electronegativity of the atom occupying the site. According to the calculated QVAL for each site of Ca ₅ Al _1.5 In _0.5 Sb ₆ , the Sb2 atomic position has the smallest QVAL, which means that the Sb2 atomic position contains the lowest electron density among the three available Sb atomic positions. means (see Table 5).

Atom Ca1 Ca2 Ca3 Al Sb1 Sb2 Sb3 Wyckoff site 4 g 4 g 2 a 4 h 4 h 4 h 4 h QVAL 2.691 2.734 2.516 2.656 4.531 4.508 4.613

Therefore, it is determined that the Sn atom (Sn=1.96 in Pauling scale) having a relatively lower electronegativity than the electronegativity of the Sb atom (Sb=2.05 in Pauling scale) will occupy the Sb2 atomic position.

The results of the present invention are summarized as follows.

1) The five-component compounds of the present invention (Ca _1.02 Yb _3.98 Al _1.48 In _0.52 Sb ₆ and Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 ) were synthesized through arc melting and post-heat treatment. In particular, Ca _1.02 Yb _3.98 Al _1.48 In _0.52 Sb ₆ containing Ca/Yb mixed atoms doped with Ca showed a phase transition from Ba ₅ Al ₂ Bi ₆ type to Ca ₅ Ga ₂ Sb ₆ type after post-heat treatment. It was confirmed that Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 containing only Ca because Ca was not substituted with Yb maintained the original Ca ₅ Ga ₂ Sb ₆ type even after post-heat treatment.

)과 상기 1 차원 음이온 사슬 사이의 공극을 채우는 세 가지 유형의 양이온 원자 위치 조합으로 설명될 수 있다. 양이온성 Ca 및 Yb의 위치 선호도는 크기 인자 기준에 의해 설명되는 반면, 음이온성 Sb 및 Sn의 위치선호도는 전자 인자 기준에 의해 설명된다.2) The isoform crystal structures of the two title compounds are the one-dimensional anionic chains (

) and the three types of cation atom position combinations that fill the voids between the one-dimensional anionic chains. The position preference of cationic Ca and Yb is explained by size factor criteria, whereas the position preference of anionic Sb and Sn is explained by electron factor criteria.

3) As a result of band structure analysis for p-type Sn-doped Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 by TB- LMTO calculation, p-type Sn increased the DOS level in _EF , which leads to an increase in electrical conductivity. . In addition, it was confirmed that the increase in the band extrema and the band degeneracy at a specific point affect the effective mass, which leads to the improvement of the Seebeck coefficient of the Sn-doped title compound.

The specific examples described herein are meant to represent preferred embodiments or examples of the present invention, and the scope of the present invention is not limited thereby. It will be apparent to those skilled in the art that modifications and other uses of the present invention do not depart from the scope of the invention as set forth in the claims herein.

Claims (6)

In the Jintle compound comprising an Al/In mixed atomic position occupied by a mixture of Al atoms and the In atoms,
the following formula;
[Formula]
Ca _{5- x} Yb _x Al _{2- y} In _y Sb _{6- z} Sn _z (0

x

3.98; 0.27

y

0.52; 0

z

0.56)
(Wherein, Ca is calcium; Yb is ytterbium; Al is aluminum; In is indium; Sb is antimony; Sn is tin.);
Jintle compound represented by .
The Jintle compound according to claim 1, wherein the Jintle compound is Ca _1.02 Yb _3.98 Al _1.48 In _0.52 Sb ₆ or Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 .
The Jintle compound according to claim 2, wherein the crystalline phase of the Jintle compound has an orthorhombic Ca ₅ Ga ₂ Sb ₆ -type (space group Pbam , Pearson code oP 26, Z = 2) structure.
According to claim 2, wherein the crystalline phase of Ca _1.02 Yb _3.98 Al _1.48 In _0.52 Sb ₆ Al and In atoms occupying mixed atomic positions of Al/In, Sb atoms occupying Sb1 atomic positions, Sb2 occupying atomic positions A one-dimensional anion chain ([(Al/In) ₂ (Sb1) ₂ (Sb2) ₂ (Sb3) ₂ ]) runs along the c-axis and runs along the c-axis, A cation atom composed of a Ca atom and Yb atom mixedly occupying a mixed atomic position, a Ca atom and a Yb atom mixed and occupying a Ca2/Yb2 mixed atomic position, and a Ca atom and a Yb atom mixed and occupying a Ca3/Yb3 mixed atomic position is 1 Jintle compound, characterized in that it fills the voids between the dimensional anion chains.
3. The method according to claim 2, wherein the crystalline phase of Ca ₅ Al _1.73 In _0.27 Sb _5.44 Sn _0.56 is an Al atom and an In atom occupying the Al/In mixed atomic position, an Sb atom occupying the Sb1 atomic position, and a Sb2/Sn mixed atom. A one-dimensional anion chain ([(Al/In) ₂ (Sb1) ₂ (Sb2/Sn) ₂ (Sb3) ₂ ]) composed of an Sb atom and Sn atom occupying a mixed position, and an Sb atom occupying an Sb3 atom position is formed. Cationic atoms running along the c-axis and comprising a Ca atom occupying the Ca1 atomic position, a Ca atom occupying the Ca2 atomic position, and a Ca atom occupying the Ca3 atomic position fill the voids between the one-dimensional anion chains mud compound.
The Jintle compound according to claim 1, wherein the Jintle compound is prepared by post-heat treatment at a temperature of 1062 to 1082 K for 5 to 9 days after being synthesized by an arc-melting method.

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