Zintl Compounds Research Articles

Electronic structure and thermoelectric performance of Zintl compound Sr3GaSb3: A first-principles study

By using first-principles method and Boltzmann theory, we simulated the thermoelectric transport properties of p-type and n-type Sr3GaSb3. It is found that the thermoelectric figure-of merit (ZT) of n-type Sr3GaSb3 is probably better than that of p-type, mainly due to its large band degeneracy. Moreover, a high ZT value of 1.74 at 850 K can be achieved for n-type Sr3GaSb3 along the yy direction, corresponding to the carrier concentration 3.5 × 1020 e cm−3. We propose that the high ZT value of experimentally synthesized p-type Sr3GaSb3 is originated from appearing of the larger number of band valley on the top of valence bands.

The relationship between the electronic structure and thermoelectric properties of Zintl compounds M2Zn5As4 (M = K, Rb)

The electronic structure and the thermoelectric properties of M2Zn5As4 (M = K, Rb) are studied by the first principles and the semiclassical BoltzTraP theory. It is determined that they are semiconductors with an indirect band gap of about 1 eV, which is much larger than that of Ca5Al2Sb6 (0.50 eV). The calculated electronic localization function indicates that they are typical Zintl bonding compounds. The combination of heavy and light bands near the valence band maximum may improve their thermoelectric performance. Rb2Zn5As4 exhibits relatively large Seebeck coefficients, high electrical conductivities, and the large "maximum" thermoelectric figures of merit (ZeT). Compared with Ca5Al2Sb6, the highest ZeT of Rb2Zn5As4 appears at relatively low carrier concentration. For Rb2Zn4As5, the p-type doping may achieve a higher thermoelectric performance than n-type doping. The thermoelectric properties of Rb2Zn5As4 are possibly superior to those of Ca5Al2Sb6.

Glass-like lattice thermal conductivity and high thermoelectric efficiency in Yb9Mn4.2Sb9

Motivated by excellent thermoelectric performance in the well-known Yb-based Zintl compounds Yb_(14)MnSb_(11) and YbZn_(2−x)Mn_xSb_2, this study investigates the thermoelectric properties of Yb_9Mn_(4.2)Sb_9. Unlike most transition metal containing Zintl phases, Yb_9Mn_(4.2)Sb)9 contains a partially occupied Mn site and thus does not have a valence-precise stoichiometry. Samples were synthesized by direct ball milling of the elements, followed by hot pressing. Consistent with previous reports, X-ray diffraction and wavelength dispersive spectroscopy confirmed a narrow composition range near Yb_9Mn_(4.2)Sb_9. High temperature measurements of the electronic properties of Yb_9Mn_(4.2)Sb_9 indicate that it is a degenerate p-type semiconductor with a band gap sufficiently large for high temperature thermoelectric applications. Hall measurements reveal that Yb_9Mn_(4.2)Sb_9 has a high extrinsic carrier concentration (~10^(20) h^+ cm^(−3)), which is due to the deviation from the theoretical “Zintl composition” of Yb_9Mn_(4.5)Sb_9. The measured carrier concentration coincides with the optimum concentration predicted using a single parabolic band model. Measurements of the thermal diffusivity and heat capacity reveal an extremely low, temperature-independent lattice thermal conductivity in this compound (κ_L < 0.4 W mK^(−1)), which is due to both the large unit cell size (44 atoms per primitive cell) and substantial disorder on the Mn site. This favorable combination of optimized electronic properties and low lattice thermal conductivity leads to a promising figure of merit at high temperature (zT = 0.7 at 950 K).

Thermoelectric Properties of Light-Element-Containing Zintl Compounds CaZn2−x Cu x P2 and CaMnZn1−x Cu x P2 (x = 0.0–0.2)

Light-element-containing CaAl2Si2-type Zintl phases CaZn2−xCuxP2 and CaMnZn1−xCuxP2 (x = 0.0–0.2) have been synthesized by solid-state reaction. Electrical resistivity (ρ), Seebeck coefficient (α), and thermal conductivity (κ) were measured over a wide temperature (T) range (80–1000 K) to evaluate the thermoelectric potential of these materials. Below 300 K, the power factor (PF; α2/ρ) is very small. Above 600 K, however, PF increases rapidly for all compositions because of a rapid increase of α and a simultaneous decrease of ρ. The measured large α is consistent with the wider band gap expected for these compositions. Compared with the pure compounds, larger PF values are observed for the Cu-substituted compounds; the largest observed PF is ∼0.5 mW/m K2. The thermal conductivity is found to be rather low, despite the presence of light elements, and is in the range 1.0–1.5 W/m K at 1000 K. Because of the combination of low κ and moderate PF values, the dimensionless figure of merit ZT = α2T/ρκ reaches a maximum of 0.4 for CaZn1.9Cu0.1P2.

The effect of Sr addition on the electrical properties of BaZn2Sb2 Zintl compounds

Sr doped BaZn2Sb2 polycrystalline materials with nominal compositions of Ba1−xSrxZn2Sb2 (x = 0.0, 0.25, 0.5) were prepared by synthesizing single crystals using a Sn-flux method followed by vacuum melting. The materials were characterized by powder X-ray diffraction and scanning electron microscopy equipped with electron energy dispersive spectroscopy, respectively. The electrical conductivity and Seebeck coefficient of the materials from room temperature to 773 K were measured. The electrical conductivity of all the materials decreased with increasing temperature and turned to increase with increasing temperature when temperature is above ~600 K, while the Seebeck coefficient increased with increasing temperature and turned to decrease with increasing temperature when temperature is above ~580 K. The electrical conductivity and Seebeck coefficient both increased after doping Sr into BaZn2Sb2. The maximum power factor for the sample with nominal composition of Ba0.5Sr0.5Zn2Sb2 reached 10.67 μW cm−1 K−2, which was about five times as high as that of the pure BaZn2Sb2.

ChemInform Abstract: Tetrahedral Framework Structures: Polymorphic Phase Transition with Reorientation of Hexagonal Helical Channels in the Zintl Compound Na2ZnSn5 and Its Relation to Na5Zn2+xSn10‐x.

AbstractTwo modifications of the new title compound, hP‐Na2ZnSn5 (I) and tI‐Na2ZnSn5 (II) are prepared from the elements at 450 and 300 °C, respectively.

Ca1–xRExAg1–ySb (RE = La, Ce, Pr, Nd, Sm; 0 ≤ x ≤1; 0 ≤ y ≤1): Interesting Structural Transformation and Enhanced High-Temperature Thermoelectric Performance

For materials used in high-temperature thermoelectric power generation, the choices are still quite limited. Here we demonstrate the design and synthesis of a new class of complex Zintl compounds, Ca(1-x)RE(x)Ag(1-y)Sb (RE = La, Ce, Pr, Nd, Sm) (P63mc, No. 186, LiGaGe-type), which exhibit a high figure of merit in the high-temperature region. Compared with the parent structure that is based on CaAgSb (Pnma, No. 62, TiNiSi-type), an interesting structural relationship is established which suggests that important size and electronic effects govern the formation of these multinary phases. According to theoretical calculations, such a structural transformation from the orthorhombic TiNiSi-type to the hexagonal LiGaGe-type also corresponds to an obvious modification in the electronic band structure, which explains the observed significant enhancement of the related thermoelectric properties. For an optimized p-type material, Ca(0.84)Ce(0.16)Ag(0.87)Sb, a figure of merit of ~0.7 can be achieved at 1079 K, which is comparable to that of Yb14MnSb11 at the same temperature. In addition, due to the excellent thermal stability and high electrical conductivity, these materials are very promising candidates for high-temperature thermoelectric power generation.

Tetrahedral Framework Structures: Polymorphic Phase Transition with Reorientation of Hexagonal Helical Channels in the Zintl Compound Na2ZnSn5 and Its Relation to Na5Zn2+xSn10–x

Two modifications of the new Zintl compound Na2ZnSn5 were synthesized by direct reactions of the elements. hP-Na2ZnSn5, which is metastable under standard conditions, is obtained by fast cooling of a melt of stoichiometric composition. Slow cooling of such a melt or tempering of hP-Na2ZnSn5 (e.g., at 300 °C) leads to the thermodynamically stable tI-Na2ZnSn5. Both phases show an open framework structure of four-bonded Zn and Sn atoms exhibiting hexagonal helical channels in which the Na atoms are situated with disorder. Whereas the Zn-Sn network of hP-Na2ZnSn5 is analogous to known Tr-Sn networks (Tr = Ga, In), tI-Na2ZnSn5 features a closely related novel framework with a different channel structure. In the structure model for hP-Na2ZnSn5 there is only one, Zn/Sn mixed occupied, site for the framework atoms, whereas Zn and Sn are fully ordered on three sites in the case of tI-Na2ZnSn5. The phase transition from hP-Na2ZnSn5 to tI-Na2ZnSn5 was studied using high-temperature powder and single-crystal X-ray diffraction methods. Na2ZnSn5 is stable up to about 350 °C and does not melt congruently but decomposes to form Na5Zn(2+x)Sn(10-x). DFT band structure calculations (TB-LMTO-ASA) were performed with ordered model structures which were deduced from a conceivable pathway for the interconversion of the two polymorphic structures of Na2ZnSn5. A band gap at the Fermi level, as expected for a Zintl phase, is found for the ordered structure of tI-Na2ZnSn5. On the basis of an analysis of the relationship between the network structures of the Sn-rich Na-Zn-Sn phases, a general perspective for novel open framework structures with exclusively four-bonded atoms is given.

High-Pressure Synthesis and Superconductivity of the Laves Phase Compound Ca(Al,Si)2 Composed of Truncated Tetrahedral Cages Ca@(Al,Si)12

The Zintl compound CaAl2Si2 peritectically decomposes to a new ternary cubic Laves phase Ca(Al,Si)2 and an Al-Si eutectic at temperatures above 750 °C under a pressure of 13 GPa. The ternary Laves phase compound can also be prepared as solid solutions Ca(Al(1-x)Si(x))2 (0.35 ≤ x ≤ 0.75) directly from the ternary mixtures under high-pressure and high-temperature conditions. The cubic Laves phase structure can be regarded as a type of clathrate compound composed of face-sharing truncated tetrahedral cages with Ca atoms at the center, Ca@(Al,Si)12. The compound with a stoichiometric composition CaAlSi exhibits superconductivity with a transition temperature of 2.6 K. This is the first superconducting Laves phase compound composed solely of commonly found elements.

On the Thermoelectric Properties of Zintl Compounds Mg3Bi2−x Pn x (Pn = P and Sb)

A series of Zintl compounds Mg3Bi2-xPnx (Pn = P and Sb) have been synthesized by the solid-state reaction method. While Sb can be substituted to a level as high as x = 1.0, P can be substituted only up to x = 0.5. The thermoelectric potential of these compounds has been evaluated by measuring resistivity (ρ), Seebeck (α) and Hall coefficients, and thermal conductivity between 80 K and 850 K. The measured resistivity and Seebeck coefficient values are consistent with those expected for small-bandgap semiconductors. Hall measurements suggest that the carriers are p type with concentration (p) increasing from ~1019 cm−3 to ~1020 cm−3 as the Bi content is increased. The Hall mobility decreases with increasing temperature (T) and reaches a more or less similar value (~45 cm2/V s) for all substituted compositions at room temperature. Due to mass defect scattering, the lattice thermal conductivity (κL) is decreased to a minimum of ~1.2 W/m K in Mg3BiSb. The power factor (α2/ρ) is found to be rather low and falls in the range 0.38 mW/m K2 to 0.66 mW/m K2. As expected, at a high temperature of 825 K, the total thermal conductivity (κ) of Mg3BiSb reaches an impressive value of ~1.0 W/m K. The highest dimensionless figure of merit (ZT) is realized for Mg3BiSb and is ~0.4 at 825 K.

Mg3Sb2-based Zintl compound: a non-toxic, inexpensive and abundant thermoelectric material for power generation

The deployment of thermoelectric materials for deriving an enhanced figure of merit (ZT) for power generation in inexpensive, non-toxic and relatively abundant bulk homogeneous solid relies on the extent of achieving the “phonon-glass electron crystal” (PGEC) characteristics. Here, a proof of principal has been established experimentally in the present work for a Zintl compound of Mg3Sb2 and its derivative of isoelectronically Bi doped Bi; Mg3Sb2−xBix (0 ≤ x ≤ 0.4) alloys in Mg3Sb2. Single phase p-type Mg3Sb2 compounds, with Mg and Sb powders as starting materials, have been prepared directly by spark plasma sintering (SPS) in a one step process. The structural refinements of this hexagonal Zintl compound by X-ray diffraction analysis (XRD) and high resolution transmission electron microscopy (HRTEM) investigation reveal that they are single phase devoid of any oxides or Sb precipitates. Transport measurements indicate low thermoelectric figure of merit (ZT = 0.26 at 750 K) for Mg3Sb2. However, an optimum doping of 0.2 at% with iso-electronic Bi ions at the Sb site enhances the ZT to 0.6 at 750 K, which is comparable with the present day industrial materials such as Bi based tellurides and selenides which are toxic. We note that the system becomes metal with carrier density exceeding 15 × 1020/cm3 for x ≥0.25. The substantial increase in ZT in Mg3Sb2−xBix (0 ≤ x ≤ 0.4) owes to a partial decoupling of the electronic and phonon subsystem, as expected for a Zintl phase compound. While the reduction in thermal conductivity in Mg3Sb2−xBix (0 ≤ x ≤ 0.4) accounts to mass fluctuations and grain boundary scattering, the enhancement in the electronic power-factor is attributed to the presence of heavy and light bands in its valence band structure. The latter has been confirmed by means of both X-ray photo electron spectroscopy studies and first-principles density functional based calculations. These measurements established that a high figure of merit can be achieved in this class of materials with appropriate doping. Further, relative abundance of the material ingredients combined with its one step synthesis leads to a cost effective production and less toxicity makes the material an environmentally benign system for thermoelectric power generation.

Improved thermoelectric properties in Zn-doped Ca5Ga2Sb6

Zintl compounds with the chemical formula Ca5M2Sb6 have attracted attention as candidates for use in thermoelectric applications due to their low thermal conductivity and promising high temperature performance (i.e., zT = 0.6 at 1000 K in Ca5Al2−xNaxSb6). We have shown previously that, relative to Ca5Al2Sb6, both Ca5Ga2Sb6 and Ca5In2Sb6 have reduced phonon velocities and improved carrier mobility, suggesting that improved zT can be achieved in these materials. Here we further investigate Ca5Ga2Sb6, which is an intrinsic semiconductor with a small concentration of p-type carriers. By substituting Zn2+ on the Ga3+ site, we show that it is possible to increase and control the carrier concentration in Ca5Ga2−xZnxSb6 and thus optimize its thermoelectric behavior. A single parabolic band model was used to estimate an effective mass of m* = 1.6me, which is slightly lower than Al-based compounds. Though the reduced m* leads to a lower Seebeck coefficient, it also leads to a much higher electronic mobility. The high mobility leads to increased thermoelectric figure of merit (zT) at low and intermediate temperatures relative to Zn-doped Ca5Al2Sb6. However, due to the decreased band gap in Ca5Ga2Sb6 relative to Ca5Al2Sb6, the maximum zT in optimally doped Ca5Ga2Sb6 is reduced (peak zT ∼ 0.35 at T = 775 K).

Synthesis, Crystal and Electronic Structures of the New Zintl phases Ba3Al3Pn5 (Pn = P, As) and Ba3Ga3P5

The new Zintl compounds Ba(3)Al(3)P(5), Ba(3)Al(3)As(5,) and Ba(3)Ga(3)P(5) have been synthesized using molten metal fluxes. They are isoelectronic and isotypic, crystallizing with a novel rhombohedral structure type in the space group R3c with unit cell constants a = 14.5886(9) Å, c = 28.990(3) Å for Ba(3)Al(3)P(5), a = 14.613(3) Å, c = 28.884(8) Å for Ba(3)Ga(3)P(5), and a = 14.9727(13) Å, c = 29.689(4) Å for Ba(3)Al(3)As(5), respectively. The structures are based on TrPn(4) (Tr = Al, Ga; Pn = P, As) tetrahedra that share both edges and corners, leading to intricate arrangements embodied in the [Tr(4)Pn(9)](15-) and [Tr(3)Pn(6)](9-) strands, interconnected by dimeric [Tr(2)Pn(6)](12-) units. The Ba(2+) cations reside within cylindrical channels within the polyanionic framework and provide the valence electrons needed for Tr-Pn covalent bonding. In spite of the large and complex structure, there are no homoatomic Tr-Tr or Pn-Pn interactions, hence, the structures can be readily rationalized in the context of the Zintl-Klemm formalism as follows [Ba(2+)](3)[Tr(3+)](3)[Pn(3-)](5); calculations on their electronic band-structures confirm this reasoning and reveal about 1.4-1.9 eV energy band gaps, that is, semiconducting behavior. Structural parallels with other known Zintl compounds are also presented.

The ESR Study of Eu Ternary Pnictides EuCd2Sb2, EuZn2As2

The magnetic properties of the Zintl compounds EuZn2As2 and EuCd2Sb2 have been studied. The measurements of resistance, magnetic susceptibility and the ESR (X band) was performed in the range 4 − 300 K. The symmetric Eu2+ ESR lines had the g-factors 2.00 (EuZn2As2), 2.03 (EuCd2Sb2) and a Lorentzian shape above 120 K. The change of shape to Gaussian indicates on the magnetic fluctuations. EuZn2As2 and EuCd2Sb2 order antiferromagnetically with the TN 16.5 and 7.4 K, respectively; but with positive Curie-Weiss temperatures. The study revealed metallic conductivity for EuCd2Sb2 and semiconductor type for EuZn2As2.

High pressure synthesis and crystal structure of a ternary superconductor Ca2Al3Si4 containing layer structured calcium sub-network isomorphous with black phosphorus

The Zintl compound CaAl2Si2 is peritectically decomposed to a mixture of Ca2Al3Si4 and aluminum metal at temperatures above 600°C under a pressure of 5GPa. The new ternary compound Ca2Al3Sl4 crystalizes with the space group Cmc21 and the lattice parameters a=5.8846(8), b=14.973(1), and c=7.7966(5)Å. The structure is composed of aluminum silicide framework [Al3Si4] and layer structured [Ca2] network interpenetrating with each other. The electron probe microanalysis (EPMA) shows the formation of solid solutions Ca2Al3−xSi4+x (x<0.6). The layer structured [Ca2] sub-network is isomorphous with black phosphorus. The new ternary compound shows superconductivity with a transition temperature (Tc) of 6.4K. The band structure calculation suggests that the superconductivity should occur through the conduction bands mainly composed of 3p orbitals of the aluminum silicide framework.

A10LaCdSb9 (A=Ca, Yb): A Highly Complex Zintl System and the Thermoelectric Properties

Two new Zintl compounds A(10)LaCdSb(9) (A=Ca, Yb), namely, Ca(9.81(1))La(0.97(1))Cd(1.23(1))Sb(9) and Yb(9.78(1))La(0.97(1))Cd(1.24(1))Sb(9), have been designed and synthesized by applying the Zintl concept. Although both compounds are isoelectronic with their Ca(11)InSb(9) and Yb(11)InSb(9) analogues, they crystallize in a new structure type with the orthorhombic space group Ibam (No.72) and feature very complex anion structures, which are composed of unique [Cd(2)Sb(6)](12-) clusters, dumbbell-shaped [Sb(2)](4-) dimers, and isolated [Sb](3-) anions. For Yb(9.78(1))La(0.97(1))Cd(1.24(1))Sb(9), an extremely low lattice thermal conductivity of 0.29 W m(-1) K(-1) was observed at 875 K, which almost approaches the lowest reported limit of nonglassy or nonionically conducting bulk materials. According to thermogravimetric (TG) and differential scanning calorimetry (DSC) analyses, both compounds show very good thermal stability and no melting or phase transition processes were found below 1173 K. Although related thermoelectric property studies on Yb(9.78(1))La(0.97(1))Cd(1.24(1))Sb(9) only present a maximum ZT of 0.11 at 920 K, owing to its low Seebeck coefficients, these materials are still very promising for their high temperature stability and low thermal conductivity. Furthermore, as mixed cations exist with different charges, it makes this system very flexible in tuning the related electrical properties.

Syntheses, crystal structure and physical properties of new Zintl phases Ba3T2As4 (T=Zn, Cd)

Through high temperature Pb-flux reactions, two new arsenide Zintl compounds, Ba3Zn2As4 and Ba3Cd2As4, were successfully obtained and their structures were accurately determined with Single-Crystal X-ray Diffraction. Both compounds are isotypic to Ba3Cd2Sb4 and crystallize in the monoclinic space group C2/m (No=12) with cell parameters of a=16.916(4)/17.089(3)Å, b=4.497(1)/4.6076(7)Å, c=7.225(2)/7.304(1)Å and β=113.147(2)/112.312(1) ° for Ba3Zn2As4 and Ba3Cd2As4, respectively. Electrical resistivity measurement on Ba3Cd2As4 reveals semiconducting behavior between 10 and 100K, which results in a very small band gap of 0.01eV. According to TG/DSC analyses, Ba3Cd2As4 exhibits good thermal stability and does not decompose below 950K.

Ca2Pd3Ge, a new fully ordered ternary Laves phase structure

The title compound, Ca2Pd3Ge, was prepared as a part of a systematic investigation of the Ca–Pd–Ge ternary phase diagram. The structure was determined and refined from single-crystal X-ray diffraction data. It is a new fully ordered ternary Laves phase with the space group R-3m, Z=3, a=5.6191 (5) Å, c=12.1674 (7) Å, wR2=0.054 (all data) and is isostructural to Mg2Ni3Si (Noréus et al., 1985 [17]) but due to the larger size of all elements in Ca2Pd3Ge, the cell axes are approximately 10% longer. The compound may formally be considered as a Zintl compound, with [Pd3Ge]4− forming a poly-anionic network and divalent Ca cations located in truncated tetrahedral interstices. The electronic structure and chemical bonding of Ca2Pd3Ge is discussed in terms of LMTO band structure calculations and compared with CaPd2 (MgCu2-type).

Soluble Zintl Phases A14ZnGe16 (A = K, Rb) Featuring [(η3-Ge4)Zn(η2-Ge4)]6– and [Ge4]4– Clusters and the Isolation of [(MesCu)2(η3,η3-Ge4)]4–: The Missing Link in the Solution Chemistry of Tetrahedral Group 14 Element Zintl Clusters

The number of Zintl phases containing polyhedral clusters of tetrel elements that are accessible for chemical reactions of the main-group element clusters is rather limited. The synthesis and structural characterization of two novel ternary intermetallic phases A(14)ZnGe(16) (A = K, Rb) are presented, and their chemical reactivity is investigated. The compounds can be rationalized as Zintl phases with 14 alkali metal cations A(+) (A = K, Rb), two tetrahedral [Ge(4)](4-) Zintl anions, and one anionic heterometallic [(Ge(4))Zn(Ge(4))](6-) cluster per formula unit. The Zn-Ge cluster comprises two (Ge(4)) tetrahedra which are linked by a Zn atom, with one (Ge(4)) tetrahedron coordinating with a triangular face (η(3)) and the other one with an edge (η(2)). [(η(3)-Ge(4))Zn(η(2)-Ge(4))](6-) is a new isomer of the [(Ge(4))Zn(Ge(4))](6-) anion in Cs(6)ZnGe(8). The phases dissolve in liquid ammonia and thus represent rare examples of soluble Zintl compounds with deltahedral units of group 14 element atoms. Compounds with tetrahedral [E(4)](4-) species have previously been isolated from solution for E = Si, Sn, and Pb, and the current investigation provides the "missing link" for E = Ge. Reaction of an ammonia solution of K(14)ZnGe(16) with MesCu (Mes = 2,4,6-(CH(3))(3)C(6)H(2)) in the presence of [18]-crown-6 (1,4,7,10,13,16-hexaoxacyclooctadecane) yielded crystals of the salt [K([18]-crown-6)](2)K(2)[(MesCu)(2)Ge(4)](NH(3))(7.5) with the polyanion [(MesCu)(2)Ge(4)](4-). This MesCu-stabilized tetrahedral [Ge(4)](4-) cluster also completes the series of [(MesCu)(2)Si(4-x)Ge(x)](4-) clusters, which have previously been isolated from solution for x = 0 and 0.7, as the end member with x = 4. The electronic structures of [(Ge(4))Zn(Ge(4))](6-) and [(MesCu)(2)Ge(4)](4-) were investigated in terms of a molecular orbital description and analyses of the electron localization functions. The results are compared with band structure calculations for the A(14)ZnGe(16) phases (A = K, Rb).

Preparation and thermoelectric properties of BaMn2−xZnxSb2 zintl compounds

Zn doped BaMn2Sb2 single crystals were synthesized by a Sn-flux method using nominal compositions of BaMn2−xZnxSb2 (x = 0.0, 0.3, 0.5, 0.7, and 1.0). The products were characterized by powder X-ray diffraction and scanning electron microscopy equipped with electron energy dispersive spectroscopy, respectively. A pure phase of BaMn2Sb2 for x = 0, a mixture of Zn doped BaMn2Sb2 and Sn for x = 0.3–0.7, and a mixture of Zn doped BaMn2Sb2, Sn and ZnSb for x = 1 were obtained. The electrical conductivity and Seebeck coefficient of the crystals from room temperature to 773 K were measured. The electrical conductivity of all the crystals increased with increasing temperature, while the Seebeck coefficient decreased with increasing temperature and approached negative values at high temperatures. The Zn doped BaMn2Sb2 crystals showed significantly higher Seebeck coefficient at low temperatures (T 550 K) than the BaMn2Sb2 single crystal.