Structural evolution of a Ge-substituted SnSe thermoelectric material with low thermal conductivity

2018 ◽  
Vol 51 (2) ◽  
pp. 337-343 ◽  
Author(s):  
Federico Serrano-Sánchez ◽  
Norbert M. Nemes ◽  
José Luis Martínez ◽  
Oscar Juan-Dura ◽  
Marco Antonio de la Torre ◽  
...  
Keyword(s):  
Phase Transition ◽  
Thermal Conductivity ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Structural Evolution ◽  
Type Structure ◽  
Scanning Calorimetry ◽  
Space Group ◽  
Low Thermal Conductivity ◽  
Structure Space

Thermoelectric materials are expected to become new alternative sources of sustainable energy. Among them, the SnSe intermetallic alloy has been described as an excellent thermoelectric compound, characterized by an extremely low thermal conductivity with maximum performance at the onset of a structural phase transition at 800 K. Recently, novel SnSe derivatives with Ge substitution have been synthesized by a direct arc-melting technique. This produces nanostructured polycrystalline samples that exhibit a record high Seebeck coefficient, anticipating an excellent performance above room temperature. Here, the structural phase transition from a GeS-type structure (space groupPnma) to a TlI-type structure (space groupCmcm) is investigatedin situ vianeutron powder diffraction (NPD) in the temperature range 298–853 K for the selected composition Sn0.8Ge0.2Se. This transition takes place at 803 K, as shown by differential scanning calorimetry. The analysis from the NPD data shows a non-monotonic behaviour of the anisotropic displacement parameters upon entering the domain of theCmcmstructure. The energies of the atomic vibrations have been quantitatively analysed by fitting the temperature-dependent mean-square displacements to Einstein oscillators. The thermal conductivity of Sn0.8Ge0.2Se is as low as 0.35 W m−1 K−1at 773 K, which mostly represents the lattice thermal contribution.

Structural phase transition in polycrystalline SnSe: a neutron diffraction study in correlation with thermoelectric properties

2016 ◽  
Vol 49 (6) ◽  
pp. 2138-2144 ◽  
Author(s):  
F. Serrano-Sánchez ◽  
N. M. Nemes ◽  
O. J. Dura ◽  
M. T. Fernandez-Diaz ◽  
J. L. Martínez ◽  
...  
Keyword(s):  
Phase Transition ◽  
Structural Phase ◽  
Neutron Diffraction Study ◽  
Type Structure ◽  
Scanning Calorimetry ◽  
Space Group ◽  
Temperature Range ◽  
Seebeck Coefficients ◽  
Structure Space ◽  
Arc Melting

SnSe has been recently reported as a promising and highly efficient thermoelectric intermetallic alloy. The present material has been prepared by arc melting, as mechanically robust pellets, consisting of highly oriented polycrystals. The evolution of its orthorhombic GeS-type structure (space groupPnma) and phase transition to TlI-type structure (space groupCmcm) at high temperature has been studiedin situby neutron powder diffraction (NPD) in the temperature range 295–873 K. This transition has been identified by differential scanning calorimetry measurements, yielding sharp peaks at 795 K. In addition, thermal transport properties were measured in a similar temperature range, and large Seebeck coefficients, as high as 1050 µV K−1at 625 K, were found. The analysis from NPD data demonstrates an almost perfect stoichiometry, Sn0.998(8)Se, that does not evolve with temperature, and a progressive decrease of the anharmonicity of the chemical bonds upon entering the domain of theCmcmstructure.

scholarly journals Structural Phase Transition and Related Thermoelectric Properties in Sn Doped AgBiSe2

Crystals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1016
Author(s):  
Xiao-Cun Liu ◽  
Ming-Yan Pan
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Thermoelectric Material ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Complex Structural

AgBiSe2, which exhibits complex structural phase transition behavior, has recently been considered as a potential thermoelectric material due to its intrinsically low thermal conductivity. In this work, we investigate the crystal structure of Sn-doped AgBiSe2 through powder X-ray diffraction and differential scanning calorimetry measurements. A stable cubic Ag1−x/2Bi1−x/2SnxSe2 phase can be obtained at room temperature when the value of x is larger than 0.2. In addition, the thermoelectric properties of Ag1−x/2Bi1−x/2SnxSe2 (x = 0.2, 0.25, 0.3, 0.35) are investigated, revealing that Ag1−x/2Bi1−x/2SnxSe2 compounds are intrinsic semiconductors with a low lattice thermal conductivity. This work provides new insights into the crystal structure adjustment of AgBiSe2 and shows that Ag1−x/2Bi1−x/2SnxSe2 is a potentially lead-free thermoelectric material candidate.

scholarly journals Struktur- und Phasenübergangsuntersuchungen an β-Li2ZnGe/ Structure and Phase Transition Investigations on β-Li2ZnGe

1981 ◽  
Vol 36 (8) ◽  
pp. 917-921 ◽  
Author(s):  
Hans-Otto Cullmann ◽  
Heinz-Walter Hinterkeuser ◽  
Hans-Uwe Schuster
Keyword(s):  
Phase Transition ◽  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Single Crystal ◽  
Ternary Compound ◽  
Type Structure ◽  
Crystal Data ◽  
Space Group ◽  
Cell Parameters ◽  
Structure Space

Abstract The ternary compound β-Li2ZnGe was prepared and its structure determined from powder and single crystal data. The compound crystallizes in a modified Na3As type structure, space group Ṗ̇̇̇̇̇̇̇̇̇̇̇̇̇̇3̄m 1 - D33d.The cell parameters are: a = 432.6 pm, c = 1647.0 pm, c/a= 3.83.A phase transition between a-and β-Li2ZnGe was found and the reaction of the elements lithium, zinc and germanium to a-Li2ZnGe was followed by differential thermal analysis. The temperatures and the enthalpies of transition and fusion were determined.

Structural phase transition, electronic, elastic, and vibrational properties of LiAl intermetallic compound: insights from first-principles calculations

2017 ◽  
Vol 95 (8) ◽  
pp. 691-698
Author(s):  
Y. Mogulkoc ◽  
Y.O. Ciftci ◽  
G. Surucu
Keyword(s):  
Phase Transition ◽  
Density Of States ◽  
Structural Phase Transition ◽  
First Principles ◽  
Density Functional ◽  
Structural Phase ◽  
Type Structure ◽  
Vibrational Properties ◽  
First Principles Calculations ◽  
Electronic Band

Using the first-principles calculations based on density functional theory (DFT), the structural, elastic, electronic, and vibrational properties of LiAl have been explored within the generalized gradient approximation (GGA) using the Vienna ab initio simulation package (VASP). The results demonstrate that LiAl compound is stable in the NaTl-type structure (B32) at ambient pressure, which is in good agreement with the experimental results and there is a structural phase transition from NaTl-type structure (B32) to CsCl-type structure (B2) at around 22.2 GPa pressure value. The pressure effects on the elastic properties have been discussed and the elastic property calculation indicates that the elastic instability could provide a phase transition driving force according to the variations relation of the elastic constant versus pressure. To gain further information about this, we also have investigated the other elastic parameters (i.e., Zener anisotropy factor, Poisson’s ratio, Young’s modulus, and isotropic shear modulus). The electronic band structure, total and partial density of states, phonon dispersion curves, and one-phonon density of states of B2 and B32 phases are also presented with results.

Reversible structural phase transition of pyridinium-4-carboxylic acid perchlorate

2010 ◽  
Vol 43 (5) ◽  
pp. 1031-1035 ◽  
Author(s):  
Heng-Yun Ye ◽  
Hong-Ling Cai ◽  
Jia-Zeng Ge ◽  
Ren-Gen Xiong
Keyword(s):  
Phase Transition ◽  
Carboxylic Acid ◽  
Structural Phase ◽  
Differential Scanning Calorimetry Measurement ◽  
Scanning Calorimetry ◽  
Reflection Index ◽  
Space Group ◽  
Cell Parameters ◽  
Bonding Effect ◽  
Reversible Phase Transition

Pyridinium-4-carboxylic acid perchlorate (C6H6NO2·ClO4) was synthesized and separated as crystals. Differential scanning calorimetry measurement shows that this compound undergoes a reversible phase transition at about 122 K with a heat hysteresis of 1.8 K. A dielectric anomaly observed at 127 K further confirms the phase transition. The low-temperature (LT;T= 103 K) structure has space groupP21/cand cell parametersa= 17.356 (6),b= 13.241 (3),c= 16.161 (7) Å, β = 138.055 (17)°. The high-temperature (HT;T= 298 K) structure has space groupP21/cand cell parametersa= 5.5046 (11),b= 13.574 (3),c= 11.834 (2) Å, β = 99.35 (3)°, but can be re-described using new axesa′ =a,b′ =b,c′ = −2a+c,V′ =Vto give the cella′ = 5.5046 (11),b′ = 13.574 (3),c′ = 17.424 (3) Å, β′ = 137.92 (3)° and space groupP21/c. The associated coordinate transformation isx′ =x+ 2z,y′ =y,z′ =zand the associated reflection index transformation ish′ =h,k′ =k,l′ =l− 2h. The relationship between the two cells is 3a,b,c(HT) approximatesa,b,c(LT). The crystal comprises one-dimensional hydrogen-bonded chains of the pyridinium-4-carboxylic acid cations and perchlorate anions. A precise analysis of the main packing and structural differences as well as the changes in the intermolecular interactions between the HT phase and the LT phase reveals that the disorder–order transition of the perchlorate anions may be the driving force of the transition, and the hydrogen-bonding effect may contribute to the transition as a secondary parameter.

scholarly journals Investigation of the structural and electronic properties of CdS under high pressure: an ab initio study

2018 ◽  
Vol 96 (2) ◽  
pp. 216-224 ◽  
Author(s):  
C. Yamcicier ◽  
Z. Merdan ◽  
C. Kurkcu
Keyword(s):  
Phase Transition ◽  
Ab Initio ◽  
Density Functional ◽  
Structural Phase ◽  
Type Structure ◽  
Ambient Conditions ◽  
Space Group ◽  
Space Groups ◽  
Intermediate States ◽  
Calculation Results

An ab initio constant pressure study is carried out to explore the behaviour of cadmium sulfide (CdS) under high hydrostatic pressure. We have studied the structural properties of CdS using density functional theory (DFT) under pressure up to 200 GPa. CdS crystallizes in a wurtzite (WZ)-type structure under ambient conditions. CdS undergoes a structural phase transition from the hexagonal WZ-type structure with space group P63mc to cubic NaCl-type structure with space group [Formula: see text]. Another phase transition is obtained from NaCl-type structure to the orthorhombic CdS-III-type structure with space group Pmmn. The first transformation proceeds via seven intermediate states with space group Cmc21, P21, Pmn21, P21/m, Pmmn, I4/mmm, and Cmcm. The latter transformation is based on two intermediate states with space groups Immm and P21/m. These phase transitions are also studied by total energy and enthalpy calculations. According to these calculations, the phase transformations occur at about 3 and 51 GPa, respectively. Calculation results on the other basic properties, such as lattice constant, volume, and bulk modulus are also compared with those of other recent theoretical and experimental data, and generally, good agreement with the available data are obtained.

scholarly journals Crystal Structures of Piperazinium Tetrahalogenometallates (II) [C4H12N2]MX4 (M = Zn, Hg; X = Br, I)

2006 ◽  
Vol 61 (1) ◽  
pp. 69-72 ◽  
Author(s):  
Hideta Ishihara ◽  
Keizo Horiuchi ◽  
Ingrid Svoboda ◽  
Hartmut Fuess ◽  
Thorsten M. Gesing ◽  
...  
Keyword(s):  
Phase Transition ◽  
Hydrogen Bond ◽  
Crystal Structures ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Lattice Stability ◽  
Space Group ◽  
Hydrogen Bond Networks

The crystal structures of piperazinium tetrahalogenometallates (II) [C4H12N2]MX4(M = Zn, Hg; X = Br, I), orthorhombic with space group P212121 and Z = 4 are isostructural with [C4H12N2]CdI4. The structure consists of piperazinium cations and isolated tetrahedralMX4 anions. [C4H12N2]ZnBr4 (1): a = 850.4(2), b = 1146.5(3), and c = 1228.4(4) pm at 300(2) K, [C4H12N2]ZnI4 (2): a = 886.89(6), b = 1209.11(9), and c = 1293.79(9) pm at 223(2) K, [C4H12N2]HgBr4 (3): a = 865.48(14), b = 1158.7(3), and c = 1233.3(2) pm at 293(2) K, [C4H12N2]HgI4 (4): a = 899.6(2), b = 1230.0(2), and c = 1299.5(3) pm at 293(2) K. All crystals show a structural phase transition at about 560 K and decomposition temperatures above 600 K. The lattice stability of the crystals is well explained by N-H · · · X hydrogen bond networks.

scholarly journals Crystal structure of mechanochemically synthesized Ag2CdSnS4

2020 ◽  
Vol 75 (4) ◽  
pp. 393-402 ◽  
Author(s):  
Eva M. Heppke ◽  
Stefan Berendts ◽  
Martin Lerch
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Powder Diffraction ◽  
Mechanochemical Synthesis ◽  
Type Structure ◽  
Structural Investigations ◽  
Space Group ◽  
X Ray ◽  
Structure Space ◽  
Acta Crystallogr

AbstractAg2CdSnS4 was synthesized by a two step mechanochemical synthesis route. From a detailed analysis of the observed reflections in the X-ray powder diffraction pattern, the crystal structure proposed in the literature (space group Cmc21 [E. Parthé, K. Yvon, R. H. Deitch, Acta Crystallogr.1969, B25, 1164–1174; O. V. Parasyuk, I. D. Olekseyuk, L. V. Piskach, S. V. Volkov, V. I. Pekhnyo, J. Alloys Compd.2005, 399, 173–177]) is questionable. Our structural investigations presented in this contribution point to the fact that Ag2CdSnS4 crystallizes in the monoclinic wurtzkesterite-type structure (space group Pn). At around T = 200°C, a phase transition to the orthorhombic wurtzstannite-type structure (space group Pmn21) is observed.

scholarly journals Inorganic Anion Regulates the Phase Transition in Two Organic Cation Salts Containing [(4-Nitroanilinium)(18-crown-6)]+ Supramolecules

2017 ◽  
Author(s):  
Yuan Chen ◽  
Yang Liu ◽  
Binzu Gao ◽  
Chuli Zhu ◽  
Zunqi Liu
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Variable Temperature ◽  
Structural Phase ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Space Group ◽  
X Ray

Two novel inorganic–organic hybrid supramolecular assemblies, namely, (4-HNA)(18-crown-6)(HSO4) (1) and (4-HNA)2(18-crown-6)2(PF6)2(CH3OH) (2) (4-HNA = 4-nitroanilinium), were synthesized and characterized by infrared spectroscopy, single X-ray diffraction, differential scanning calorimetry (DSC), and temperature-dependent dielectric measurements. The two compounds underwent reversible phase transitions at about 255 K and 265 K, respectively. These phase transitions were revealed and confirmed by the thermal anomalies in DSC measurements and abrupt dielectric anomalies during heating. The phase transition may have originated from the [(4-HNA)(18-crown-6)]+ supramolecular cation. The inorganic anions tuned the crystal packings and thus influenced the phase-transition points and types. The variable-temperature X-ray diffraction data for crystal 1 revealed the occurrence of a phase transition in the high-temperature phase with the space group of P21/c and in the low-temperature phase with the space group of P21/n. Crystal 2 exhibited the same space group P21/c at different temperatures. The results indicated that crystals 1 and 2 both underwent an iso-structural phase transition.

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