Zintl phase compounds AM2Sb2 （A=Ca, Sr, Ba, Eu, Yb;M=Zn, Cd） is a new class of promising thermoelectrics owing to their intrinsic features in electronic and crystal structure, such as a small or even disappeared ban...Zintl phase compounds AM2Sb2 （A=Ca, Sr, Ba, Eu, Yb;M=Zn, Cd） is a new class of promising thermoelectrics owing to their intrinsic features in electronic and crystal structure, such as a small or even disappeared band-gap, large density-of-states at the Fermi level, covalently bonded network of M-Sb, as well as the layered stacking by cations A2＋and anionic slabs （M2Sb2）2-. In addi-tion, the rich solid-state chemistry of Zintl phase allows structural modification and chemical substitution to adjust the fundamental transport parameters （carrier concentration, mobility, effective mass, electronic and lattice thermal conductivity） for improving the thermoelectric performance. In the present review, the recent advances in synthesis and thermoelectric characterization of title com-pounds AM2Sb2 were presented, and the effects of alloying or substitution for sites A, M and Sb on the electrical and thermal trans-port were emphasized. The structural disorder yielded by the incorporation of multiple ions significantly increased the thermoelectric figure of merit mainly resulted from the reduction of thermal conductivity without disrupting the carrier transport region in substance. Therefore, alloying or substitution has been a feasible and common route utilized to enhance thermoelectric properties in these Zintl phase compounds, especially for YbZn0.4Cd1.6Sb2 （ZT700 K=1.26）, EuZn1.8Cd0.2Sb2 （ZT650 K=1.06）, and YbCd1.85Mn0.15Sb2 （ZT650 K=1.14）.展开更多
In this work the structural,electronic and thermoelectric properties of YbMg_(2)X_(2)(X=P,As,Sb,Bi)zintl compounds were investigated comprehensively using first principles study.The electronic properties were studied ...In this work the structural,electronic and thermoelectric properties of YbMg_(2)X_(2)(X=P,As,Sb,Bi)zintl compounds were investigated comprehensively using first principles study.The electronic properties were studied using PBE GGA,TB-mBJ and hybrid(YS-PBE0)potentials.All the structural parameters of optimized structures are in harmonious agreement to the available data.The band structure study illustrates that the titled materials manifest metallic and semi metallic nature using PBE and TB-mBJ potentials while they show wide band gap semiconducting behavior by following hybrid(YS-PBE0)potential.Total density of states(TDOS)and partial density of states(PDOS)were also calculated to glimpse the contribution of orbitals of atoms in the formation of bands.Transport properties were studied by using BoltzTraP2 code employed to WIEN2k.We get enormous values of Seebeck coefficient(S),power factor(PF)and thermoelectric figure of merit(ZT)for all the samples YbMg_(2)X_(2)(X=P,As,Sb,Bi),Moreover,the overwhelming transport properties for the titled compounds indicate the optimum level of carriers’concentration which pinpoints these materials to be better thermoelectrics in the 1-2-2 zintl family.展开更多
We report here the synthesis and characterization of two new members of the M2 E 12 family of endohe-dral Zintl clusters,[Fe_(2)Sn_(4)Bi_(8)]^(3-)and[Cr_(2)Sb_(12)]^(3-),both of which contain open-shell metal dimers e...We report here the synthesis and characterization of two new members of the M2 E 12 family of endohe-dral Zintl clusters,[Fe_(2)Sn_(4)Bi_(8)]^(3-)and[Cr_(2)Sb_(12)]^(3-),both of which contain open-shell metal dimers encap-sulated inside a triple-decker cluster of main-group atoms.The 75-electron[Fe_(2)Sn_(4)Bi_(8)]^(3-)cluster has a D4h-symmetric structure,while[Cr_(2)Sb_(12)]^(3-),despite having the same 75-electron count,is strongly dis-torted to a geometry that resembles a CrSb_(8)crown capped by a CrSb_(4)unit.The structural differences between the two are driven by the increasing availability of 3d electron density in the earlier transi-tion metal,which leads,ultimately,to different electronic configurations in the two clusters.The trends precisely mirror those observed in the ME_(10)and ME_(12)families containing a single transition metal ion.展开更多
Gaining an understanding of the growth mechanism from single atoms to clusters and bulk materials continues to present a challenge.Thus,it is important to explore the evolving trends of clusters in the structure and p...Gaining an understanding of the growth mechanism from single atoms to clusters and bulk materials continues to present a challenge.Thus,it is important to explore the evolving trends of clusters in the structure and properties during the size evolution.In this work,we report the synthesis and characterization of two medium-sized chain-like polyarsenic anions.[As_(21)]^(3-)represents a trimeric example of polyarsenic anion assembled through oxidative coupling of As_(7)^(3-)anions.The anion As_(18)^(4-)included in[As_(18)MO_(2)(CO)_(8)]^(4-)is regarded as formed by two realgar-type As_(8)subunits connected by a dinuclear AsAs dumbbell.The As_(18)cluster was previously predicted by theory,and this is the first time successfully synthesized using wet chemistry method.Besides,small-sized polyarsenides As_(2)^(2-)and As_(10)^(2-)were found in compound[K(18-crown-6)]_(3)[As_(10)]_(0.5)[As_(4){Mo(CO)_(3)}_(2)]_(0.5)·2en.Among these,the former exhibits coordination with metal atoms.Single-crystal X-ray diffraction combined with quantum chemical calculations revealed the formation of double bonded As_(2)^(2-)stabilized by metal carbonyl groups.This work demonstrates a novel synthetic approach for the preparation of new polyarsenides and highlights their intriguing bonding characteristics,laying the foundation for the synthesis of such compounds and paving the way for their potential applications.展开更多
Mg_(3)Sb_(1.5)Bi_(0.5)-based Zintl compounds have attracted extensive attention as potential thermoelectric materials due to their earth-abundant elements.However,pure and intrinsic Mg_(3)Sb_(1.5)Bi_(0.5)manifests a p...Mg_(3)Sb_(1.5)Bi_(0.5)-based Zintl compounds have attracted extensive attention as potential thermoelectric materials due to their earth-abundant elements.However,pure and intrinsic Mg_(3)Sb_(1.5)Bi_(0.5)manifests a poor thermoelectric performance because of its low electrical conductivity of about 3×10^(2)S/m at room temperature.In this work,In and Se co-doping was carried out to optimize the thermoelectric perfor-mance of n-type Mg_(3)Sb_(1.5)Bi_(0.5)-based material.The experimental results revealed that the carrier con-centration and mobility of Mg_(3)Sb_(1.5)Bi_(0.5)significantly increased after In and Se co-doping,leading to an improvement of power factor.Simultaneously,lattice thermal conductivity was significantly reduced due to the large mass difference between In and Mg.A maximum zT of 1.64 at 723 K was obtained for the Mg_(3.17)In_(0.03)Sb_(1.5)Bi_(0.49)Se_(0.01)sample.And an average zT value of about 1.1 between 300 and 723 K was achieved,which insures its possible application at medium temperature range as a non-toxic and low-cost TE material.展开更多
The Zintl compound Mg3Sb2 has been recently identified as promising thermoelectric material owing to its high thermoelectric performance and cost-effective,nontoxicity and environment friendly characteristics.However,...The Zintl compound Mg3Sb2 has been recently identified as promising thermoelectric material owing to its high thermoelectric performance and cost-effective,nontoxicity and environment friendly characteristics.However,the intrinsically p-type Mg3Sb2 shows low figure of merit（z T = 0.23 at 723 K） for its poor electrical conductivity.In this study,a series of Mg（3-x）LixSb2 bulk materials have been prepared by high-energy ball milling and spark plasma sintering（SPS） process.Electrical transport measurements on these materials revealed significant improvement on the power factor with respect to the undoped sample,which can be essentially attributed to the increased carrier concentration,leading to a maximum z T of0.59 at 723 K with the optimum doping level x = 0.01.Additionally,the engineering z T and energy conversion efficiency are calculated to be 0.235 and 4.89%,respectively.To our best knowledge,those are the highest values of all reported p-type Mg3Sb2-based compounds with single element doping.展开更多
Polycrystalline samples of Zintl phase EuCd2-xMnxSb2 （0.05≤x≤0.6） with the CaAl2Si2-type crystal structure （space group P3ml） were synthesized via a solid-state reaction followed by suitable cooling, annealing a...Polycrystalline samples of Zintl phase EuCd2-xMnxSb2 （0.05≤x≤0.6） with the CaAl2Si2-type crystal structure （space group P3ml） were synthesized via a solid-state reaction followed by suitable cooling, annealing and spark plasma sintering （SPS） processes. In samples with x=0.0, 0.1, 0.2, 0.4 and 0.6, the electrical conductivity, Seebeck coefficient, and thermal conductivity were performed as a function of temperature from 300 to 650 K. It was found that chemical substitution of Mn failed to optimize the thermoelectric properties of p-type conductive EuCd2Sb2. It was because that the Mn substitution induced the minority carriers （electrons）, resulting in decreasing the electrical conductivity drastically despite the fact that it enlarged the Seebeck coefficient and reduced the thermal conductivity synchronously.展开更多
1-2-2-type Zintl phase compound has aroused great interest for potential thermoelectric applications.However,YbMg_(2)Sb_(2) is seldom studied due to the very low electrical conductivity resulting from the large differ...1-2-2-type Zintl phase compound has aroused great interest for potential thermoelectric applications.However,YbMg_(2)Sb_(2) is seldom studied due to the very low electrical conductivity resulting from the large difference in the electronegativity between Mg and Sb.In this paper,we adjust the covalently bonded network of MgeSb by replacing part of the Mg with Zn which has the electronegativity closer to that of Sb.The decreased polarity in the anionic framework offers more free distance for electrons for the enhanced Hall mobility and electrical conductivity.Together with the increased point defect and the decreased lattice thermal conductivity by introduction of Zn,the maximum ZT value of ~0.8 at 773 K is achieved in YbMg_(0.9)Zn_(1.1)Sb_(2) which is~100% enhancement compared with that of YbMg_(2)Sb_(2).展开更多
To investigate the reactivity of homoatomic clusters[E_(9)]^(4-)(E=Si-Pb)and intermetalloid clusters[M@E_(9)]^(q-),the reactions of the Zintl anions[Sn_(9)]^(4-) and[Ni@Sn_(9)]^(4-) with the CdMes_(2)(Mes=Mesitylene)i...To investigate the reactivity of homoatomic clusters[E_(9)]^(4-)(E=Si-Pb)and intermetalloid clusters[M@E_(9)]^(q-),the reactions of the Zintl anions[Sn_(9)]^(4-) and[Ni@Sn_(9)]^(4-) with the CdMes_(2)(Mes=Mesitylene)in the presence of 2.2.2-crypt were carried out.Two new compounds[K(2.2.2-crypt)]_(6)[(Sn_(9))Cd(Sn_(9))]·en(1)and[K(2.2.2-crypt)]_(6)[(Ni@Sn_(9))Cd(Ni@Sn_(9))]·en(2)were afforded.Both 1 and 2 were characterized by single-crystal X-ray diffraction,energy dispersive X-ray(EDX),and electrospray ionization mass spectrometry(ESI-MS),and can be viewed as two[Sn_(9)]^(4-)or[Ni@Sn_(9)]^(4-)subunits bridged by Cd ion in an η^(3):η^(3) coordination mode.Quantum chemical calculations reveal the relationships between the geometries and electronic structures of clusters 2a,[Ni_(3)Ge_(18)]^(4-)and[Cu_(4)@Sn_(18)]^(4-).Further electron localization technique(Ad NDP method)was performed to explain chemical bonding patterns of 1a.展开更多
RE 3Cu 3Sb 4(RE=Nd, Sm, Tb, Dy, Ho) was synthesized by arc melting method and their crystal structures were characterized by powder X ray method. The compounds crystallize in cubic system, Y 3Au 3Sb 4 type, sp...RE 3Cu 3Sb 4(RE=Nd, Sm, Tb, Dy, Ho) was synthesized by arc melting method and their crystal structures were characterized by powder X ray method. The compounds crystallize in cubic system, Y 3Au 3Sb 4 type, space group I43d (No.220), Pearson code cI40. The unit cell parameters are: Nd 3Cu 3Sb 4: a =0 96749(1) nm, V =0 90561(3) nm 3; Sm 3Cu 3Sb 4: a =0 96145(1) nm, V =0 88875(3) nm 3; Tb 3Cu 3Sb 4: a =0 95362(1) nm, V =0 86721(3) nm 3; Dy 3Cu 3Sb 4: a =0 95088(1) nm, V =0 85975(3) nm 3; Ho 3Cu 3Sb 4: a =0 9488(2) nm, V =0 8541(5) nm 3; Z =4. The structures are characterized by covalent bonded Cu Sb tetrahedra which form three dimensional networks by sharing corners. The rare earth atoms are distributed in the cages. The formula with the charge balance can be written as RE 3+ 3Cu 1+ 3Sb 3- 4 which are metallic Zintl phases having the weak metallic conductivity. The bonds have typical transitional features. General atomic coordination environment rules are followed. The unit cell parameters show the lanthanide contraction.展开更多
Antimony-based Zintl compounds AM2Sb2(A=Ca,Sr,Ba,Yb,Eu;M=Mg,Zn,Cd,Mn),which enable a broad range of manipulation on electrical and thermal transport properties,are considered as an important class of thermoelectric ma...Antimony-based Zintl compounds AM2Sb2(A=Ca,Sr,Ba,Yb,Eu;M=Mg,Zn,Cd,Mn),which enable a broad range of manipulation on electrical and thermal transport properties,are considered as an important class of thermoelectric materials.Phonon and carrier transport engineering were realized in YbMg2Sb2 via equivalent and aliovalent substitution of Zn and Ag,respectively.The roomtemperature thermal conductivity reduces from 1.96 to 1.15 W m^-1 K^-1 for YbMg2-xZnxSb2 due to the mass and strain fluctuation through the formation of the absolute solid solution of YbMg2Sb2-YbZn2Sb2.Furthermore,the carrier concentration has been further optimized by Ag doping(from 0.42×10^19 to 7.72×10^19 cm^-3 at room temperature),and thus the electrical conductivity and the power factor are enhanced effectively.The integrated aspects make the dimensionless figure of merit(zT)reach 0.48 at 703 K,which is 60%higher than the pristine YbMgZnSb2 sample.展开更多
A new ternary cluster anion [Au（η^2-Sn2Sb2）2]^3- was synthesized and identified. The electronic structure of[Au（η^2-Sn2Sb2）2]^3- was analyzed by means of DFT calculations. The electronic energy and energy gap in...A new ternary cluster anion [Au（η^2-Sn2Sb2）2]^3- was synthesized and identified. The electronic structure of[Au（η^2-Sn2Sb2）2]^3- was analyzed by means of DFT calculations. The electronic energy and energy gap indicate that [Au（η^2-Sn2Sb2）2]^3- features coplanar faces AuSn_2 in which gold is directly coordinated by four tin atoms. Molecule orbital composition analysis indicates that d-orbital in Au atom contributes to bonding. Charge decomposition analysis（CDA） shows that electron donation and back donation are the key factors forming planar conformation of Au atom in [Au（η^2-Sn2Sb2）2]^3-. Meanwhile, the calculated Mayer bond order indicates relatively weaker interactions between Au and coordinated tetrahedral [Sn2Sb2]^2-.展开更多
A new complex K0.5[K（18-crown-6）]1.5Geg.1.5en （1） which contains unpreceden- ted ＂up＂ and ＂down＂ chain arrangement of unit [-（Ge9-K-Ge9）3-] has been prepared by the reaction of K4Ge9 with HgS in ethylenediam...A new complex K0.5[K（18-crown-6）]1.5Geg.1.5en （1） which contains unpreceden- ted ＂up＂ and ＂down＂ chain arrangement of unit [-（Ge9-K-Ge9）3-] has been prepared by the reaction of K4Ge9 with HgS in ethylenediamine （en） in the presence of 18-crown-6（1,4,7,10,13,16- hexaoxacyclooctadecane）, and characterized by X-ray structure analysis. The color of the title crystals （black）, which is darker than that of the reported three compounds with chains of germanium clusters, may result from the naked K＋ and their interactions with the chain. And the structure differences between 1 and the reported three compounds with chains of germanium have also been discussed.展开更多
The effect of replacing the anion from N to Bi down the group in the periodic table is investigated on SrMg2X2（X = N,P,As,Sb,Bi）.A full potential linearized augmented plane wave plus local orbitals method is used al...The effect of replacing the anion from N to Bi down the group in the periodic table is investigated on SrMg2X2（X = N,P,As,Sb,Bi）.A full potential linearized augmented plane wave plus local orbitals method is used along with different exchange–correlation potentials to obtain the lattice constants,phonons,electronic,and optical properties of the Sr Mg2X2（X = N,P,As,Sb,Bi） Zintl compounds.A good agreement is achieved and our calculations are validated by previous experimental and theoretical data.All compounds have shown stable dynamical behavior with gamma centered longitudinal response having no imaginary frequencies.Electronic band structures reveal the semiconducting nature of the compounds.The Pnictogen（X）-p state contributed mainly in the valence band and the Sr-d state forms the conduction of the compounds.Relative charge transfer and low overlapping of the atomic densities indicates the preferable ionic bonding character of these materials.In the optical properties,real and imaginary parts of dielectric function,complex refractive index,birefringence,reflectivity,and optical conductivity are calculated.These compounds can be utilized in the optical and optoelectronic devices.展开更多
The title complex [K（2,2,2-crypt）]3Sb11 has been prepared by the reaction of K3Cd2Sb with Cu-C≡CH in ethylenediamine in the presence of 2,2,2-crypt, and characterized by low temperature X-ray structure analysis. Th...The title complex [K（2,2,2-crypt）]3Sb11 has been prepared by the reaction of K3Cd2Sb with Cu-C≡CH in ethylenediamine in the presence of 2,2,2-crypt, and characterized by low temperature X-ray structure analysis. The crystal is of orthorhombic system, space group C2221 with a = 15.475（3）, b = 22.807（5）, c = 24.834（6）, V = 8765（3）3, Dc = 1.960 g/cm3, C54H108K3N6O18Sb11, Mr = 2586.01, F（000） = 4944, μ = 3.531 mm-1, Z = 4, R = 0.0442 and wR = 0.1053 for 10265 observed reflections （I 2σ（I））. The ＂naked＂ Sb113- anion is stable due to the completely sequestered alkali metal cations through ion-ion interactions.展开更多
We investigated the transport properties of isoelectronic substitution of Yb by Ca for Zintl phase YbCd2Sb2 below 300 K.The p-type Yb1-xCaxCd2Sb2(0.2≤x≤0.8) samples were synthesized via a solid-state reaction follow...We investigated the transport properties of isoelectronic substitution of Yb by Ca for Zintl phase YbCd2Sb2 below 300 K.The p-type Yb1-xCaxCd2Sb2(0.2≤x≤0.8) samples were synthesized via a solid-state reaction followed by suitable cooling,annealing,grinding,and spark plasma sintering(SPS) densification processes.For samples with x=0.2,0.4,0.5,0.6,0.8,the electrical conductivity,Seebeck coefficient,thermal conductivity,heat capacity and Hall effect measurements were carried out in the temperature range from 1...展开更多
The undecaphosphide anion in ethylenediamine/18-crown-6 solution is isolated as [K（18-crown-6）]3P11·2en 1. The crystal structure has been determined by single-crystal X-ray diffraction. The crystal is of monocl...The undecaphosphide anion in ethylenediamine/18-crown-6 solution is isolated as [K（18-crown-6）]3P11·2en 1. The crystal structure has been determined by single-crystal X-ray diffraction. The crystal is of monoclinic, space group P21 with α = 13.4731（7）, b = 16.1123（6）, c = 16.5117（9） A, β = 112.133（2）°, Y = 3320.3（3） A3, Dc = 1.371 g/cm^3, C40H88K3N4O18P11, Mr = 1371.11, F（000） = 1444,μ = 0.532 mm^-1, Z= 2, R = 0.0544 and wR = 0.1326 for 11423 observed reflections （I 〉 20（I））. The ＂naked＂ P11^3- ion is stabilized by two partly sequestered potassiums, The third partly sequestered potassium does not interact with the P atom （P（6）） but with two solvent molecules.展开更多
The endohedral plumbaspherene cluster anion [Rh@Pbl2]3- was synthesized by the reaction of K4Pb9 with Rh（PPh3）3Cl in ethylenediamine （en） solution in the presence of 18-crown-6 （1,4,7,10,13,16-hexaoxacyclooctadec...The endohedral plumbaspherene cluster anion [Rh@Pbl2]3- was synthesized by the reaction of K4Pb9 with Rh（PPh3）3Cl in ethylenediamine （en） solution in the presence of 18-crown-6 （1,4,7,10,13,16-hexaoxacyclooctadecane）, and characterized by single-crystal X-ray diffraction and energy-dispersive X-ray （EDX） analysis. The novel zintl ion cluster [Rh@Pbl2]^- represents the first structurally characterized plumbaspherene Pb12 cluster with Ih point symmetry encapsulating a group 9 element in a spherical tetrel deltahedron. And the discovery of anion [Rh@Pb12]3- also provides direct proof for previous reports on the observation of [M@Pb12]x± （clusters in mass spectrometric experiments proved by quantum-chemical calculations）. DFT computations indicate that the icosahedral cluster anion [Rh@Pb12]3- is isostructural and isoelectronic with [Ir@Sn12]3-.展开更多
Polyarsenides containing coinage metals,[As_(7)Cu(PPh_(3))]^(2-)(1)and[M_(2)As_(14)]^(4-)(M=Cu,2;Ag,3),were synthesized by reactions of the nominal composition K_(3)As_(7) with Group 11 metal complexes.The possible in...Polyarsenides containing coinage metals,[As_(7)Cu(PPh_(3))]^(2-)(1)and[M_(2)As_(14)]^(4-)(M=Cu,2;Ag,3),were synthesized by reactions of the nominal composition K_(3)As_(7) with Group 11 metal complexes.The possible intermediate,cluster 1,was isolated from the solution phase through subtle changes in reaction conditions in the formation process of complex 2.Hence,we establish the pathway of the bimetallic bridged clusters[Cu_(2)As_(14)]^(4-)by the oxidation of the[As_(7)Cu(PPh_(3))]^(2-).Quantum chemical calculations reveal the presence of metallophilic interaction in clusters 2 and 3.展开更多
Bi_(2)Te_(3) based alloys have been the most widely used thermoelectric material at low temperature for many decades.Here we report Se doped n-type Mg_(3)Bi_(2) based materials with a thermoelectric figure-of-merit ZT...Bi_(2)Te_(3) based alloys have been the most widely used thermoelectric material at low temperature for many decades.Here we report Se doped n-type Mg_(3)Bi_(2) based materials with a thermoelectric figure-of-merit ZT of 0.82 at 300 K and a peak ZT of 1.24 at 498 K,which is comparable to the n-type Bi_(2)Te_(3) and Te doped Mg_(3)Bi_(1.4)Sb_(0.6).The improved thermoelectric performance is benefited from the high carrier concentration and mobility as well as the thermal conductivity reduction.The reduced resistivity increased the power factor at all measured temperatures,leading to a higher engineering ZT(ZTeng)and engineering power factor(PFeng)for n-type Mg_(3)Bi_(2).The n-type Mg_(3)Bi_(1.4)Sb_(0.6) materials are promising for thermoelectric power generation and cooling applications near room temperature.展开更多
基金supported by National Basic Research Program of China(2007CB607503)National Natural Science Foundation of China(50821004,10979069)
文摘Zintl phase compounds AM2Sb2 （A=Ca, Sr, Ba, Eu, Yb;M=Zn, Cd） is a new class of promising thermoelectrics owing to their intrinsic features in electronic and crystal structure, such as a small or even disappeared band-gap, large density-of-states at the Fermi level, covalently bonded network of M-Sb, as well as the layered stacking by cations A2＋and anionic slabs （M2Sb2）2-. In addi-tion, the rich solid-state chemistry of Zintl phase allows structural modification and chemical substitution to adjust the fundamental transport parameters （carrier concentration, mobility, effective mass, electronic and lattice thermal conductivity） for improving the thermoelectric performance. In the present review, the recent advances in synthesis and thermoelectric characterization of title com-pounds AM2Sb2 were presented, and the effects of alloying or substitution for sites A, M and Sb on the electrical and thermal trans-port were emphasized. The structural disorder yielded by the incorporation of multiple ions significantly increased the thermoelectric figure of merit mainly resulted from the reduction of thermal conductivity without disrupting the carrier transport region in substance. Therefore, alloying or substitution has been a feasible and common route utilized to enhance thermoelectric properties in these Zintl phase compounds, especially for YbZn0.4Cd1.6Sb2 （ZT700 K=1.26）, EuZn1.8Cd0.2Sb2 （ZT650 K=1.06）, and YbCd1.85Mn0.15Sb2 （ZT650 K=1.14）.
基金the Deanship of Scientific Research at King Khalid University for funding this work through General Research Project under grant number(R.G.P2/139/43)。
文摘In this work the structural,electronic and thermoelectric properties of YbMg_(2)X_(2)(X=P,As,Sb,Bi)zintl compounds were investigated comprehensively using first principles study.The electronic properties were studied using PBE GGA,TB-mBJ and hybrid(YS-PBE0)potentials.All the structural parameters of optimized structures are in harmonious agreement to the available data.The band structure study illustrates that the titled materials manifest metallic and semi metallic nature using PBE and TB-mBJ potentials while they show wide band gap semiconducting behavior by following hybrid(YS-PBE0)potential.Total density of states(TDOS)and partial density of states(PDOS)were also calculated to glimpse the contribution of orbitals of atoms in the formation of bands.Transport properties were studied by using BoltzTraP2 code employed to WIEN2k.We get enormous values of Seebeck coefficient(S),power factor(PF)and thermoelectric figure of merit(ZT)for all the samples YbMg_(2)X_(2)(X=P,As,Sb,Bi),Moreover,the overwhelming transport properties for the titled compounds indicate the optimum level of carriers’concentration which pinpoints these materials to be better thermoelectrics in the 1-2-2 zintl family.
基金supported by the National Natural Science Foundation of China(Nos.92161102,21971118)the Natural Science Foundation of Tianjin City(Nos.21JCZXJC00140,20JCYBJC01560)the 111 Project(No.B18030)from Ministry of Education China
文摘We report here the synthesis and characterization of two new members of the M2 E 12 family of endohe-dral Zintl clusters,[Fe_(2)Sn_(4)Bi_(8)]^(3-)and[Cr_(2)Sb_(12)]^(3-),both of which contain open-shell metal dimers encap-sulated inside a triple-decker cluster of main-group atoms.The 75-electron[Fe_(2)Sn_(4)Bi_(8)]^(3-)cluster has a D4h-symmetric structure,while[Cr_(2)Sb_(12)]^(3-),despite having the same 75-electron count,is strongly dis-torted to a geometry that resembles a CrSb_(8)crown capped by a CrSb_(4)unit.The structural differences between the two are driven by the increasing availability of 3d electron density in the earlier transi-tion metal,which leads,ultimately,to different electronic configurations in the two clusters.The trends precisely mirror those observed in the ME_(10)and ME_(12)families containing a single transition metal ion.
基金supported by the National Natural Science Foundation of China(Nos.92161102,21971118 to Z.-M.Sun)the Natural Science Foundation of Tianjin City(Nos.20JCYBJC01560 and 21JCZXJC00140 to Z.-M.Sun)+1 种基金the Fundamental Research Program of Shanxi Province(No.202203021222248)the Taiyuan Normal University College Students Science and Technology Innovation Project(No.CXCY2278)。
文摘Gaining an understanding of the growth mechanism from single atoms to clusters and bulk materials continues to present a challenge.Thus,it is important to explore the evolving trends of clusters in the structure and properties during the size evolution.In this work,we report the synthesis and characterization of two medium-sized chain-like polyarsenic anions.[As_(21)]^(3-)represents a trimeric example of polyarsenic anion assembled through oxidative coupling of As_(7)^(3-)anions.The anion As_(18)^(4-)included in[As_(18)MO_(2)(CO)_(8)]^(4-)is regarded as formed by two realgar-type As_(8)subunits connected by a dinuclear AsAs dumbbell.The As_(18)cluster was previously predicted by theory,and this is the first time successfully synthesized using wet chemistry method.Besides,small-sized polyarsenides As_(2)^(2-)and As_(10)^(2-)were found in compound[K(18-crown-6)]_(3)[As_(10)]_(0.5)[As_(4){Mo(CO)_(3)}_(2)]_(0.5)·2en.Among these,the former exhibits coordination with metal atoms.Single-crystal X-ray diffraction combined with quantum chemical calculations revealed the formation of double bonded As_(2)^(2-)stabilized by metal carbonyl groups.This work demonstrates a novel synthetic approach for the preparation of new polyarsenides and highlights their intriguing bonding characteristics,laying the foundation for the synthesis of such compounds and paving the way for their potential applications.
基金supported by the Chunhui Program of the Education Ministry of China,and that at the University of Electronic Science and Technology of China was funded by the Department of Science and Technology of Sichuan Province(2021JDTD0030)the National Natural Science Foundation of China(No.62104032,No.62174022).
文摘Mg_(3)Sb_(1.5)Bi_(0.5)-based Zintl compounds have attracted extensive attention as potential thermoelectric materials due to their earth-abundant elements.However,pure and intrinsic Mg_(3)Sb_(1.5)Bi_(0.5)manifests a poor thermoelectric performance because of its low electrical conductivity of about 3×10^(2)S/m at room temperature.In this work,In and Se co-doping was carried out to optimize the thermoelectric perfor-mance of n-type Mg_(3)Sb_(1.5)Bi_(0.5)-based material.The experimental results revealed that the carrier con-centration and mobility of Mg_(3)Sb_(1.5)Bi_(0.5)significantly increased after In and Se co-doping,leading to an improvement of power factor.Simultaneously,lattice thermal conductivity was significantly reduced due to the large mass difference between In and Mg.A maximum zT of 1.64 at 723 K was obtained for the Mg_(3.17)In_(0.03)Sb_(1.5)Bi_(0.49)Se_(0.01)sample.And an average zT value of about 1.1 between 300 and 723 K was achieved,which insures its possible application at medium temperature range as a non-toxic and low-cost TE material.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.U1601213 and 51572287)the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences(Grant No.QYZDB-SSW-SLH013)
文摘The Zintl compound Mg3Sb2 has been recently identified as promising thermoelectric material owing to its high thermoelectric performance and cost-effective,nontoxicity and environment friendly characteristics.However,the intrinsically p-type Mg3Sb2 shows low figure of merit（z T = 0.23 at 723 K） for its poor electrical conductivity.In this study,a series of Mg（3-x）LixSb2 bulk materials have been prepared by high-energy ball milling and spark plasma sintering（SPS） process.Electrical transport measurements on these materials revealed significant improvement on the power factor with respect to the undoped sample,which can be essentially attributed to the increased carrier concentration,leading to a maximum z T of0.59 at 723 K with the optimum doping level x = 0.01.Additionally,the engineering z T and energy conversion efficiency are calculated to be 0.235 and 4.89%,respectively.To our best knowledge,those are the highest values of all reported p-type Mg3Sb2-based compounds with single element doping.
基金Project supported by Young Eastern Scholar Project of Shanghai Municipal Education Commission(QD2015031)
文摘Polycrystalline samples of Zintl phase EuCd2-xMnxSb2 （0.05≤x≤0.6） with the CaAl2Si2-type crystal structure （space group P3ml） were synthesized via a solid-state reaction followed by suitable cooling, annealing and spark plasma sintering （SPS） processes. In samples with x=0.0, 0.1, 0.2, 0.4 and 0.6, the electrical conductivity, Seebeck coefficient, and thermal conductivity were performed as a function of temperature from 300 to 650 K. It was found that chemical substitution of Mn failed to optimize the thermoelectric properties of p-type conductive EuCd2Sb2. It was because that the Mn substitution induced the minority carriers （electrons）, resulting in decreasing the electrical conductivity drastically despite the fact that it enlarged the Seebeck coefficient and reduced the thermal conductivity synchronously.
基金funded by the National Natural Science Foundation of China(11674078,24401019,51871077,and 51871081)the National Nature Science Foundation of Guangdong Province of China(2018A0303130033)+3 种基金Shenzhen fundamental research projects(JCYJ20170811155832192,JCYJ20160608161000821)Shenzhen Science and Technology Innovation Plan(KQISCX20180328165435202,JQJSCX20180328165656256)Startup Foundation from ShenzhenStartup Foundation from Harbin Institute of Technology(Shenzhen).
文摘1-2-2-type Zintl phase compound has aroused great interest for potential thermoelectric applications.However,YbMg_(2)Sb_(2) is seldom studied due to the very low electrical conductivity resulting from the large difference in the electronegativity between Mg and Sb.In this paper,we adjust the covalently bonded network of MgeSb by replacing part of the Mg with Zn which has the electronegativity closer to that of Sb.The decreased polarity in the anionic framework offers more free distance for electrons for the enhanced Hall mobility and electrical conductivity.Together with the increased point defect and the decreased lattice thermal conductivity by introduction of Zn,the maximum ZT value of ~0.8 at 773 K is achieved in YbMg_(0.9)Zn_(1.1)Sb_(2) which is~100% enhancement compared with that of YbMg_(2)Sb_(2).
基金supported by the National Natural Science Foundation of China(Nos.92161102 and 21971118)the Natural Science Foundation of Tianjin City(Nos.20JCYBJC01560 and B2021202077)to Z.-M.Sun。
文摘To investigate the reactivity of homoatomic clusters[E_(9)]^(4-)(E=Si-Pb)and intermetalloid clusters[M@E_(9)]^(q-),the reactions of the Zintl anions[Sn_(9)]^(4-) and[Ni@Sn_(9)]^(4-) with the CdMes_(2)(Mes=Mesitylene)in the presence of 2.2.2-crypt were carried out.Two new compounds[K(2.2.2-crypt)]_(6)[(Sn_(9))Cd(Sn_(9))]·en(1)and[K(2.2.2-crypt)]_(6)[(Ni@Sn_(9))Cd(Ni@Sn_(9))]·en(2)were afforded.Both 1 and 2 were characterized by single-crystal X-ray diffraction,energy dispersive X-ray(EDX),and electrospray ionization mass spectrometry(ESI-MS),and can be viewed as two[Sn_(9)]^(4-)or[Ni@Sn_(9)]^(4-)subunits bridged by Cd ion in an η^(3):η^(3) coordination mode.Quantum chemical calculations reveal the relationships between the geometries and electronic structures of clusters 2a,[Ni_(3)Ge_(18)]^(4-)and[Cu_(4)@Sn_(18)]^(4-).Further electron localization technique(Ad NDP method)was performed to explain chemical bonding patterns of 1a.
文摘RE 3Cu 3Sb 4(RE=Nd, Sm, Tb, Dy, Ho) was synthesized by arc melting method and their crystal structures were characterized by powder X ray method. The compounds crystallize in cubic system, Y 3Au 3Sb 4 type, space group I43d (No.220), Pearson code cI40. The unit cell parameters are: Nd 3Cu 3Sb 4: a =0 96749(1) nm, V =0 90561(3) nm 3; Sm 3Cu 3Sb 4: a =0 96145(1) nm, V =0 88875(3) nm 3; Tb 3Cu 3Sb 4: a =0 95362(1) nm, V =0 86721(3) nm 3; Dy 3Cu 3Sb 4: a =0 95088(1) nm, V =0 85975(3) nm 3; Ho 3Cu 3Sb 4: a =0 9488(2) nm, V =0 8541(5) nm 3; Z =4. The structures are characterized by covalent bonded Cu Sb tetrahedra which form three dimensional networks by sharing corners. The rare earth atoms are distributed in the cages. The formula with the charge balance can be written as RE 3+ 3Cu 1+ 3Sb 3- 4 which are metallic Zintl phases having the weak metallic conductivity. The bonds have typical transitional features. General atomic coordination environment rules are followed. The unit cell parameters show the lanthanide contraction.
基金supported by the National Key Research and Development Program of China (2018YFA0702100)the National Natural Science Foundation of China (21771123)+2 种基金the Programme of Introducing Talents of Discipline to Universities (D16002)the Science and Technology Commission of Shanghai Municipality (15DZ2260300)Key Laboratory of Optoelectronic Materials Chemistry and Physics, Chinese Academy of Sciences (2008DP173016)
文摘Antimony-based Zintl compounds AM2Sb2(A=Ca,Sr,Ba,Yb,Eu;M=Mg,Zn,Cd,Mn),which enable a broad range of manipulation on electrical and thermal transport properties,are considered as an important class of thermoelectric materials.Phonon and carrier transport engineering were realized in YbMg2Sb2 via equivalent and aliovalent substitution of Zn and Ag,respectively.The roomtemperature thermal conductivity reduces from 1.96 to 1.15 W m^-1 K^-1 for YbMg2-xZnxSb2 due to the mass and strain fluctuation through the formation of the absolute solid solution of YbMg2Sb2-YbZn2Sb2.Furthermore,the carrier concentration has been further optimized by Ag doping(from 0.42×10^19 to 7.72×10^19 cm^-3 at room temperature),and thus the electrical conductivity and the power factor are enhanced effectively.The integrated aspects make the dimensionless figure of merit(zT)reach 0.48 at 703 K,which is 60%higher than the pristine YbMgZnSb2 sample.
基金supported by National Natural Science Foundation of China(21171162).Thanks for Computing center of Jilin Province
文摘A new ternary cluster anion [Au（η^2-Sn2Sb2）2]^3- was synthesized and identified. The electronic structure of[Au（η^2-Sn2Sb2）2]^3- was analyzed by means of DFT calculations. The electronic energy and energy gap indicate that [Au（η^2-Sn2Sb2）2]^3- features coplanar faces AuSn_2 in which gold is directly coordinated by four tin atoms. Molecule orbital composition analysis indicates that d-orbital in Au atom contributes to bonding. Charge decomposition analysis（CDA） shows that electron donation and back donation are the key factors forming planar conformation of Au atom in [Au（η^2-Sn2Sb2）2]^3-. Meanwhile, the calculated Mayer bond order indicates relatively weaker interactions between Au and coordinated tetrahedral [Sn2Sb2]^2-.
基金Supported by the National Natural Science Foundation of China(No.21003125,21073190)the Natural Science Foundation of Fujian Province(2010 J01057)
文摘A new complex K0.5[K（18-crown-6）]1.5Geg.1.5en （1） which contains unpreceden- ted ＂up＂ and ＂down＂ chain arrangement of unit [-（Ge9-K-Ge9）3-] has been prepared by the reaction of K4Ge9 with HgS in ethylenediamine （en） in the presence of 18-crown-6（1,4,7,10,13,16- hexaoxacyclooctadecane）, and characterized by X-ray structure analysis. The color of the title crystals （black）, which is darker than that of the reported three compounds with chains of germanium clusters, may result from the naked K＋ and their interactions with the chain. And the structure differences between 1 and the reported three compounds with chains of germanium have also been discussed.
基金Project supported by a grant from the"Research Center of Female Scientific and Medical Colleges",the Deanship of Scientific Research,King Saud UniversityYaseen M is thankful to Higher Education Commission(HEC)+1 种基金Pakistan for funding(Grant No.6410/Punjab/NRPU/R&D/HEC/2016)the support of the United States Government and the American people through the United States Agency for International Development(USAID)
文摘The effect of replacing the anion from N to Bi down the group in the periodic table is investigated on SrMg2X2（X = N,P,As,Sb,Bi）.A full potential linearized augmented plane wave plus local orbitals method is used along with different exchange–correlation potentials to obtain the lattice constants,phonons,electronic,and optical properties of the Sr Mg2X2（X = N,P,As,Sb,Bi） Zintl compounds.A good agreement is achieved and our calculations are validated by previous experimental and theoretical data.All compounds have shown stable dynamical behavior with gamma centered longitudinal response having no imaginary frequencies.Electronic band structures reveal the semiconducting nature of the compounds.The Pnictogen（X）-p state contributed mainly in the valence band and the Sr-d state forms the conduction of the compounds.Relative charge transfer and low overlapping of the atomic densities indicates the preferable ionic bonding character of these materials.In the optical properties,real and imaginary parts of dielectric function,complex refractive index,birefringence,reflectivity,and optical conductivity are calculated.These compounds can be utilized in the optical and optoelectronic devices.
基金supported by the Key Research Project of CAS (KJCX2-EW-01)the National Natural Science Foundation of China (20173190)the Natural Science Foundation of Fujian Province (2010J01057)
文摘The title complex [K（2,2,2-crypt）]3Sb11 has been prepared by the reaction of K3Cd2Sb with Cu-C≡CH in ethylenediamine in the presence of 2,2,2-crypt, and characterized by low temperature X-ray structure analysis. The crystal is of orthorhombic system, space group C2221 with a = 15.475（3）, b = 22.807（5）, c = 24.834（6）, V = 8765（3）3, Dc = 1.960 g/cm3, C54H108K3N6O18Sb11, Mr = 2586.01, F（000） = 4944, μ = 3.531 mm-1, Z = 4, R = 0.0442 and wR = 0.1053 for 10265 observed reflections （I 2σ（I））. The ＂naked＂ Sb113- anion is stable due to the completely sequestered alkali metal cations through ion-ion interactions.
基金supported by the National Basic Research Program of China (2007CB607503)National Natural Science Foundation of China (50821004)the MPG-CAS Partner Group
文摘We investigated the transport properties of isoelectronic substitution of Yb by Ca for Zintl phase YbCd2Sb2 below 300 K.The p-type Yb1-xCaxCd2Sb2(0.2≤x≤0.8) samples were synthesized via a solid-state reaction followed by suitable cooling,annealing,grinding,and spark plasma sintering(SPS) densification processes.For samples with x=0.2,0.4,0.5,0.6,0.8,the electrical conductivity,Seebeck coefficient,thermal conductivity,heat capacity and Hall effect measurements were carried out in the temperature range from 1...
基金This work was supported by the National Natural Science Foundation of China (No. 20473092)
文摘The undecaphosphide anion in ethylenediamine/18-crown-6 solution is isolated as [K（18-crown-6）]3P11·2en 1. The crystal structure has been determined by single-crystal X-ray diffraction. The crystal is of monoclinic, space group P21 with α = 13.4731（7）, b = 16.1123（6）, c = 16.5117（9） A, β = 112.133（2）°, Y = 3320.3（3） A3, Dc = 1.371 g/cm^3, C40H88K3N4O18P11, Mr = 1371.11, F（000） = 1444,μ = 0.532 mm^-1, Z= 2, R = 0.0544 and wR = 0.1326 for 11423 observed reflections （I 〉 20（I））. The ＂naked＂ P11^3- ion is stabilized by two partly sequestered potassiums, The third partly sequestered potassium does not interact with the P atom （P（6）） but with two solvent molecules.
基金supported by the National Natural Science Foundation of China(No.21473200)
文摘The endohedral plumbaspherene cluster anion [Rh@Pbl2]3- was synthesized by the reaction of K4Pb9 with Rh（PPh3）3Cl in ethylenediamine （en） solution in the presence of 18-crown-6 （1,4,7,10,13,16-hexaoxacyclooctadecane）, and characterized by single-crystal X-ray diffraction and energy-dispersive X-ray （EDX） analysis. The novel zintl ion cluster [Rh@Pbl2]^- represents the first structurally characterized plumbaspherene Pb12 cluster with Ih point symmetry encapsulating a group 9 element in a spherical tetrel deltahedron. And the discovery of anion [Rh@Pb12]3- also provides direct proof for previous reports on the observation of [M@Pb12]x± （clusters in mass spectrometric experiments proved by quantum-chemical calculations）. DFT computations indicate that the icosahedral cluster anion [Rh@Pb12]3- is isostructural and isoelectronic with [Ir@Sn12]3-.
基金supported by the National Natural Science Foundation of China(21971118 to Z.-M.S.).
文摘Polyarsenides containing coinage metals,[As_(7)Cu(PPh_(3))]^(2-)(1)and[M_(2)As_(14)]^(4-)(M=Cu,2;Ag,3),were synthesized by reactions of the nominal composition K_(3)As_(7) with Group 11 metal complexes.The possible intermediate,cluster 1,was isolated from the solution phase through subtle changes in reaction conditions in the formation process of complex 2.Hence,we establish the pathway of the bimetallic bridged clusters[Cu_(2)As_(14)]^(4-)by the oxidation of the[As_(7)Cu(PPh_(3))]^(2-).Quantum chemical calculations reveal the presence of metallophilic interaction in clusters 2 and 3.
基金supported by Young Scientist Fund of National Natural Science Foundation of China(No.51601152)Chunhui Program from Education Ministry of China,Open Research Subject of Key Laboratory of Fluid and Power Machinery of Ministry of Education(No.SZJJ2017-082)the Sichuan Science and Technology Program(No.2019JDTD0024).
文摘Bi_(2)Te_(3) based alloys have been the most widely used thermoelectric material at low temperature for many decades.Here we report Se doped n-type Mg_(3)Bi_(2) based materials with a thermoelectric figure-of-merit ZT of 0.82 at 300 K and a peak ZT of 1.24 at 498 K,which is comparable to the n-type Bi_(2)Te_(3) and Te doped Mg_(3)Bi_(1.4)Sb_(0.6).The improved thermoelectric performance is benefited from the high carrier concentration and mobility as well as the thermal conductivity reduction.The reduced resistivity increased the power factor at all measured temperatures,leading to a higher engineering ZT(ZTeng)and engineering power factor(PFeng)for n-type Mg_(3)Bi_(2).The n-type Mg_(3)Bi_(1.4)Sb_(0.6) materials are promising for thermoelectric power generation and cooling applications near room temperature.
