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1. Advancing the Ca ₁₄ AlSb ₁₁ Structure Type: Synthesis and Characterization of Yb ₁₄ CdSb ₁₁ for Thermoelectric Applications

   https://doi.org/10.1002/zaac.202500015  

   Opara, Ivan Chinonso; Fettinger, James C; Star, Kurt E; Bux, Sabah K; Shen, Zihao; Taufour, Valentin; Kauzlarich, Susan M (April 2025, Zeitschrift für anorganische und allgemeine Chemie)

   The ternary phase, Yb14CdSb11, has been synthesized by flux and polycrystalline methods. The crystal structure is determined via single-crystal X-ray diffraction, revealing that it crystallizes in the Ca14AlSb11 structure type (I41/acd space group with unit cell parameters of a = 16.5962(2) & Aring; and c = 22.1346(5) & Aring;, 90 K, Z = 8, R1 = 2.65%, and wR2 = 4.58%). The polycrystalline form of the compound is synthesized from a stoichiometric reaction of Yb4Sb3, CdSb, Yb, and Sb. The elemental composition is confirmed using scanning electron microscopy and energy-dispersive spectroscopy, and phase purity is verified by powder X-ray diffraction. Thermoelectric measurements, including resistivity, Seebeck coefficient, thermal conductivity, Hall carrier concentration, and Hall mobility, are conducted from 300 to 1273 K. Yb14CdSb11 exhibits a peak zT = 0.90 at 1200 K. Carrier concentration and Hall mobility range from 6.99 x 1020-1.01 x 1021 cm-3 and 4.45-9.35 x 10-1 cm2 V-1 s-1, respectively. This carrier concentration is lower than that reported for the Zn or Mn analogs leading to a lower thermoelectric figure of merit at high temperatures. However, with appropriate doping, this phase should also be a promising p-type candidate for high-temperature energy conversion applications. 

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2. The impact of site selectivity and disorder on the thermoelectric properties of Yb ₂₁ Mn ₄ Sb ₁₈ solid solutions: Yb ₂₁ Mn _4−x Cd _x Sb ₁₈ and Yb _21−y Ca _y Mn ₄ Sb ₁₈

   https://doi.org/10.1039/d1ma00497b  

   He, Allan; Cerretti, Giacomo; Kauzlarich, Susan M. (August 2021, Materials Advances)

   Thermoelectric materials can convert heat into electricity. They are used to generate electricity when other power sources are not available or to increase energy efficiency by recycling waste heat. The Yb 21 Mn 4 Sb 18 phase was previously shown to have good thermoelectric performance due to its large Seebeck coefficient (∼290 μV K −1 ) and low thermal conductivity (0.4 W m −1 K −1 ). These characteristics stem respectively from the unique [Mn 4 Sb 10 ] 22− subunit and the large unit cell/site disorder inherent in this phase. The solid solutions, Yb 21 Mn 4− x Cd x Sb 18 ( x = 0, 0.5, 1.0, 1.5) and Yb 21− y Ca y Mn 4 Sb 18 ( y = 3, 6, 9, 10.5) have been prepared, their structures characterized and thermoelectric properties from room temperature to 800 K measured. A detailed look into the structural disorder for the Cd and Ca solid solutions was performed using synchrotron powder X-ray diffraction and pair distribution function methods and shows that these are highly disordered structures. The substitution of Cd gives rise to more metallic behavior whereas Ca substitution results in high resistivity. As both Cd and Ca are isoelectronic substitutions, the changes in properties are attributed to changes in the electronic structure. Both solid solutions show that the thermal conductivities remain extremely low (∼0.4 W m −1 K −1 ) and that the Seebeck coefficients remain high (>200 μV K −1 ). The temperature dependence of the carrier mobility with increased Ca substitution, changing from approximately T −1 to T −0.5 , suggests that another scattering mechanism is being introduced. As the bonding changes from polar covalent with Yb to ionic for Ca, polar optical phonon scattering becomes the dominant mechanism. Experimental studies of the Cd solid solutions result in a max zT of ∼1 at 800 K and, more importantly for application purposes, a ZT avg ∼ 0.6 from 300 K to 800 K. 

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3. Crystal structure characterization and electronic structure of a rare-earth-containing Zintl phase in the Yb–Al–Sb family: Yb ₃ AlSb ₃

   https://doi.org/10.1107/S2053229621005192  

   Shang, Rongqing; Nguyen, An T.; He, Allan; Kauzlarich, Susan M. (June 2021, Acta Crystallographica Section C Structural Chemistry)

   null (Ed.)

   A rare-earth-containing compound, ytterbium aluminium antimonide, Yb 3 AlSb 3 (Ca 3 AlAs 3 -type structure), has been successfully synthesized within the Yb–Al–Sb system through flux methods. According to the Zintl formalism, this structure is nominally made up of (Yb 2+ ) 3 [(Al 1− )( 1b – Sb 2− ) 2 ( 2b – Sb 1− )], where 1b and 2b indicate 1-bonded and 2-bonded, respectively, and Al is treated as part of the covalent anionic network. The crystal structure features infinite corner-sharing AlSb 4 tetrahedra, [AlSb 2 Sb 2/2 ] 6− , with Yb 2+ cations residing between the tetrahedra to provide charge balance. Herein, the synthetic conditions, the crystal structure determined from single-crystal X-ray diffraction data, and electronic structure calculations are reported. 

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4. One cation makes a difference: structure-thermoelectric interplay in pseudo-rock salt intermetallic Eu5-xAxAl3Sb6 (A = Sr and Yb)

   https://doi.org/10.5061/dryad.mkkwh71f1  

   Garay, Luis; Borgsmiller, Leah; Zavanelli, Duncan; Snyder, G Jeffrey; Fettinger, James; Kauzlarich, Susan (January 2026, Dryad)

   Abstract: Single crystals of Eu5-xYbxAl3Sb6 and Eu5-x-ySrxYbyAl3Sb6 were synthesized by flux methods and their structures determined by single-crystal X-ray diffraction, confirming the monoclinic C2/m symmetry. The Al content in these phases can be increased from 3 to 4 by metallurgical mixing of the elements to form polycrystalline powders. A comparative study of polycrystalline synthesized Eu5Al4Sb6 and its Sr- and Yb-substituted solid solutions, along with the pseudo-quinary phase Eu2.5Sr2Yb0.5Al4Sb6, is presented. Substituting Eu2+ with the more ionic Sr2+ enhances mobility and increases the magnitude of the Seebeck coefficient, while the more covalent Yb2+ drives the system metallic, lowering Seebeck values but improving zT to 0.8 at 873 K. The quinary phase further suppresses bipolar conduction, delaying the high-temperature downturn observed in both ternary solid solutions. Across all compositions, thermal conductivities remain exceptionally low (<1 W m⁻¹ K⁻¹), enabling promising figures of merit. Methods: The datasets (Powder X-ray diffraction and Thermoelectric property measurements) for the phase pure powders are provided. Compositions are provided below. Synthesis: Phase pure powders of composition Eu_5.08Al₄Sb₄, Eu₅Al₄Sb₆, Eu_5-xA_xAl₄Sb₆ (A = Sr: x = 0.5, 2.5, 5; A = Yb: x = 0.5, 1, 1.5, 2, 5) and Eu_2.5Sr₂Yb_0.5Al₄Sb₆ Powder X-ray Diffraction (PXRD): PXRD data were collected at room temperature in air on ground single crystals and bulk powders of both solid solutions using a Bruker D8 Advance Eco diffractometer with Cu Kα radiation, 1000 W (40 kV, 25 mA), over 2θ = 15–85°, with a step size of 0.02°, and a scan rate of 1 s per step. Polycrystalline samples and ground single crystals were prepared on a zero-background holder using isopropanol. Thermal Conductivity Thermal Diffusivity (D) was measured on thin (1.19 to 1.2 mm thick) slices of Eu_5-xAxAl4Sb₆ (A = Sr and Yb) pellets using a Netzsch LFA 457 Microflash under a flow of high-purity Ar with a polished piece of Zr ribbon wrapped around the sample holder to act as an oxygen catcher. The thermal conductivity (κ) was determined using the equation: κ = D x ρ x C_p. The Dulong-Petit heat capacity value, C_p, was calculated from 3R/atom (R = gas constant).  The pellets’ density (ρ) was measured in replicate using the Archimedes method with toluene as the liquid. All samples were > 95% of their theoretical crystallographic densities, calculated using the Arrhenius method. Electrical Resistivity and Seebeck A Linseis LSR-3 instrument was used to measure resistivity and the Seebeck coefficient employing the four-probe method from 350 K to 800 K under a He atmosphere. The instrument was calibrated with a constantan standard before use. The sample geometries were bar-shaped (10.5 mm x 4 mm x 2 mm) and polished before measurements with 8 mm probes. Multiple samples were measured to ensure reproducibility, and the data were cross-checked with measurements taken at Northwestern University. At Northwestern, electrical resistivity and Hall effect data were measured using a home-built Hall instrument. This set-up uses a four-point van der Pauw resistivity measurement with molybdenum leads and a current of 100 mA. Seebeck coefficient data were collected using a home-built two-probe Seebeck instrument with chromel/Nb thermocouples. TechnicalInfo: # One cation makes a difference: structure-thermoelectric interplay in pseudo-rock salt intermetallic Eu5-*x*A*x*Al3Sb6 (A = Sr and Yb) Dataset DOI: [10.5061/dryad.mkkwh71f1](https://doi.org/10.5061/dryad.mkkwh71f1) ## Description of the data and file structure **PXRD data collection (located in folder PXRD)** PXRD data were collected at room temperature in air on ground single crystals and bulk powders of both solid solutions using a Bruker D8 Advance Eco diffractometer with Cu Kα radiation, 1000 W (40 kV, 25 mA), over 2θ = 15–85°, with a step size of 0.02°, and a scan rate of 1 s per step. Polycrystalline samples were prepared on a zero-background holder using isopropanol. **Thermal Conductivity (located in folder TE properties)** Thermal Diffusivity (*D)* was measured on thin (1.19 to 1.2 mm thick) slices of Eu5-*x*A*x*Al4Sb6 (A = Sr and Yb) pellets using a Netzsch LFA 457 Microflash under a flow of high-purity Ar with a polished piece of Zr ribbon wrapped around the sample holder to act as an oxygen catcher. The thermal conductivity (κ) was determined using the equation: κ = *D* x ρ x C~p~. The Dulong-Petit heat capacity value, C~p~, was calculated from 3*R*/atom (R = gas constant).  The pellets’ density (ρ) was measured in replicate using the Archimedes method with toluene as the liquid. All samples were > 95% of their theoretical crystallographic densities, calculated using the Arrhenius method. **Electrical Resistivity, Seebeck, and Hall Data Collection** A Linseis LSR-3 instrument was used to measure resistivity and the Seebeck coefficient employing the four-probe method from 350 K to 800 K under a He atmosphere. The instrument was calibrated with a constantan standard before use. The sample geometries were bar-shaped (10.5 mm x 4 mm x 2 mm) and polished before measurements with 8 mm probes. Multiple samples were measured to ensure reproducibility, and the data were cross-checked with measurements taken at Northwestern University. At Northwestern, electrical resistivity and Hall effect data were measured using a home-built Hall instrument. This set-up uses a four-point van der Pauw resistivity measurement with molybdenum leads and a current of 100 mA. Seebeck coefficient data were collected using a home-built two-probe Seebeck instrument with chromel/Nb thermocouples. ### Files and variables #### File: EuSrYbAlSb6_ChemMater_D.zip **Description:** There are 2 folders for each type of data: Powder X-ray Diffraction (**PXRD**) data for the polycrystalline synthesized samples indicated above; (**TE Properties**) Thermoelectric properties provides the electrical resistivity and Seebeck coefficient as a function of temperature for the polycrystalline samples. #### PXRD folder has 3 sub-folders: EuYbSr, Sr, Yb. The sub-folders contain dataset (.cvs) indicated by the cation composition of the polycrystalline synthesized sample. **Sub-Folder** **EuYbSr**: contains the PXRD data for Eu~2.5~Sr~2~Yb~0.5~Al~4~Sb~6~ **Sub-Folder** **Sr**: contains the PXRD data for Eu~2.5~Sr~2.5~Al~4~Sb~6~; Eu~4.5~Sr~0.5~Al~4~Sb~6~; Sr~5~Al~4~Sb~6~ **Sub-Folder** **Yb**: contains the PXRD data for Yb~5~Al~4~Sb~6;~ Eu~4~Yb~1~Al~4~Sb~6~; Eu~3~Yb~2~Al~4~Sb~6~; Eu~3.5~Yb~1.5~Al~4~Sb~6~; Eu~4.5~Yb~0.5~Al~4~Sb~6~ Each *.cvs dataset is indicated by the sample composition. Each dataset contains a header with the composition; column 1: 2-theta (degree); column 2: intensity (arbitrary units (a.u.)). #### **TE** **Properties** folder has 4 sub-folders: **Eu,** **EuYbSr**, **Sr**, **Yb**. The sub-folders contain dataset (*.cvs) indicated by the cation composition of the polycrystalline synthesized sample. Each *.cvs file has the composition of the element in the A column, and Temperature/K and Resistivity/ mOhm•cm; Seebeck Coefficient/ µV/K; Thermal Conductivity/W •m^-1^ •K^-1^ and ( if collected) carrier concentration/ h/cm^3^ and Hall mobility /cm^2^•V^-1^•s^-1^ **Sub-Folder Eu**: contains TE data for Eu~5~Al~4~Sb~6~; Eu~5.08~Al~4~Sb~6~; **Sub-Folder EuYbSr:** contains TE data for Eu~2.5~Sr~2.0~Yb~0.5~Al~4~Sb~6~ **Sub-Folder Sr:** contains TE data for Sr~5~Al~4~Sb~6~; Eu~2.5~Sr~2.5~Al~4~Sb~6~; Eu~4.5~Sr~0.5~Al~4~Sb~6~; **Sub-Folder Yb:** contains TE data for Yb~5~Al~4~Sb~6;~ Eu~4~Yb~1~Al~4~Sb~6~; Eu~3~Yb~2~Al~4~Sb~6~; Eu~3.5~Yb~1.5~Al~4~Sb~6~; Eu~4.5~Yb~0.5~Al~4~Sb~6~; #### 

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5. The effect of Mg ₃ As ₂ alloying on the thermoelectric properties of n-type Mg ₃ (Sb, Bi) ₂

   https://doi.org/10.1039/D1DT01600H  

   Imasato, Kazuki; Anand, Shashwat; Gurunathan, Ramya; Snyder, G. Jeffrey (July 2021, Dalton Transactions)

   Mg 3 Sb 2 –Mg 3 Bi 2 alloys have been heavily studied as a competitive alternative to the state-of-the-art n-type Bi 2 (Te,Se) 3 thermoelectric alloys. Using Mg 3 As 2 alloying, we examine another dimension of exploration in Mg 3 Sb 2 –Mg 3 Bi 2 alloys and the possibility of further improvement of thermoelectric performance was investigated. While the crystal structure of pure Mg 3 As 2 is different from Mg 3 Sb 2 and Mg 3 Bi 2 , at least 15% arsenic solubility on the anion site (Mg 3 ((Sb 0.5 Bi 0.5 ) 1−x As x ) 2 : x = 0.15) was confirmed. Density functional theory calculations showed the possibility of band convergence by alloying Mg 3 Sb 2 –Mg 3 Bi 2 with Mg 3 As 2 . Because of only a small detrimental effect on the charge carrier mobility compared to cation site substitution, the As 5% alloyed sample showed zT = 0.6–1.0 from 350 K to 600 K. This study shows that there is an even larger composition space to examine for the optimization of material properties by considering arsenic introduction into the Mg 3 Sb 2 –Mg 3 Bi 2 system. 

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