The cationic clathrate Si46−2xP2xTex crystal growth by chemical vapour transport

Philipp, Frauke; Schmidt, Peer

doi:10.1016/j.jcrysgro.2008.09.001

Cited by 18 publications

(5 citation statements)

References 21 publications

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“…The frequency distribution is significantly larger than that in other cationic type I clathrates Sn 17 Zn 7 P 22 X 8 with X = Br, I (from 100 to 230 ppm) and type III clathrates Si 172- x P x Te y (−300 to 200 ppm) . The 31 P NMR signal of sample Si 30 P 16 Te 8 prepared by chemical transport at significantly lower temperatures (800 K) covers a much smaller frequency range (−250 ≤ δ ≤ 150 ppm). We attribute a much broader frequency range for Si 32.5(5) P 13.2(1) Te 6.65(5) to the large amount of disorder present in the title compound.…”

Section: Resultsmentioning

confidence: 98%

Cationic Clathrate I Si_46-xP_xTe_y (6.6(1) ≤ y ≤ 7.5(1), x ≤ 2y): Crystal Structure, Homogeneity Range, and Physical Properties

et al. 2009

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A new cationic clathrate I Si(46-x)P(x)Te(y) (6.6(1) < or = y < or = 7.5(1), x < or = 2y at 1375 K) was synthesized from the elements and characterized by X-ray powder diffraction, thermal analysis, scanning electron microscopy, wavelength dispersive X-ray spectroscopy (WDXS), neutron powder diffraction, and (31)P NMR spectroscopy. The thermal behaviors of the magnetic susceptibility and resistivity were investigated as well. Si(46-x)P(x)Te(y) reveals a wide homogeneity range due to the presence of vacancies in the tellurium guest positions inside the smaller cage of the clathrate I structure. The vacancy ordering in the structure of Si(46-x)P(x)Te(y) causes the change of space group from Pm3n (ideal clathrate I) to Pm3 accompanied by the redistribution of P and Si atoms over different framework positions. Neutron powder diffraction confirmed that P atoms preferably form a cage around the vacancy-containing tellurium guest position. Additionally, (31)P NMR spin-spin relaxation experiments revealed the presence of sites with different coordination of phosphorus atoms. Precise determination of the composition of Si(46-x)P(x)Te(y) by WDXS showed slight but noticeable deviation (x < or = 2y) of phosphorus content from the Zintl counting scheme (x = 2y). The compound is diamagnetic while resistivity measurements show activated behavior or that of heavily doped semiconductors. Thermal analysis revealed high stability of the investigated clathrate: Si(46-x)P(x)Te(y) melts incongruently at approximately 1460 K in vacuum and is stable in air against oxidation up to 1295 K.

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Section: Resultsmentioning

confidence: 98%

Cationic Clathrate I Si_46-xP_xTe_y (6.6(1) ≤ y ≤ 7.5(1), x ≤ 2y): Crystal Structure, Homogeneity Range, and Physical Properties

et al. 2009

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“…[28,29] Compared to the SiP compound, even less experimental work is published on the thermodynamic properties of SiP 2 . Only Philipp and Schmidt [30] mentioned that the heat capacity was determined by DSC measurements as C p (SiP 2 ) = {67.0(2) + 17.1(4)910 À3 T} J/K/mol. However, they did not give any experimental detail.…”

Section: Thermodynamic Datamentioning

confidence: 99%

Modeling of Thermodynamic Properties and Phase Equilibria of the Si-P System

Liang

Schmid–Fetzer

2013

J. Phase Equilib. Diffus.

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A Calphad assessment of the Si-P system is performed based on critical review of all available original experimental thermodynamic and phase equilibrium data. It is demonstrated that a simple disordered substitutional solution model is sufficient for the liquid phase and that previous assumptions of short-range ordering in the Si-P liquid phase may not be justified. Alternative model descriptions for the Gibbs energy of the (Si) solid solution phase were developed to reveal the consequences in describing the largely scattering solid solubility data of P in (Si). Two alternative sets of consistently calculated phase boundaries of the (Si) phase are shown. It is impossible to reconcile the only experimental (Si) solidus data with the solvus data from the same work.

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“…This group of compounds is called cationic (inverse) clathrates. The first representatives (Ge 38 A 8 X 8 : A = P, As, Sb; X = Cl, Br, I) were prepared by Menke and von Schnering. − Recently several cationic clathrates with Sn, Ge, Si, Zn, Cu, P, or As forming the frameworks and halogenide or chalcogenide ions as guests were described. − …”

Section: Introductionmentioning

confidence: 99%

“…The recent significant interest in clathrate compounds is caused by their perspective as thermoelectric materials . From this point of view, the recently described cationic clathrates I of the ternary Si–P–Te system − are the most interesting, as they combine high thermal and chemical stability with the promising values of the thermoelectric figure of merit …”

Section: Introductionmentioning

confidence: 99%

Homo- and Heterovalent Substitutions in the New Clathrates I Si₃₀P₁₆Te_8–xSe_x and Si_30+xP_16–xTe_8–xBr_x: Synthesis, Crystal Structure, and Thermoelectric Properties

Abramchuk¹,

Carrillo‐Cabrera²,

Veremchuk³

et al. 2012

Inorg. Chem.

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The new cationic clathrates I Si(30)P(16)Te(8-x)Se(x) and Si(30+x)P(16-x)Te(8-x)Br(x) were synthesized by the standard ampule technique. The Si(30)P(16)Te(8-x)Se(x) (x = 0-2.3) clathrates crystallize in the cubic space group Pm3̅n with the unit cell parameter a ranging from 9.9382(2) to 9.9696(1) Å. In the case of the Si(30+x)P(16-x)Te(8-x)Br(x) (x = 1-6.4) clathrates, the lattice parameter varies from 9.9720(8) to 10.0405(1) Å; at lower Si/P ratios (x = 1-3) the ordering of bromine atoms induces the splitting of the guest positions and causes the transformation from the space group Pm3n to Pm3. Irrespective of the structure peculiarities, the normal temperature motion of the guest atoms inside the oversized cages of the framework is observed. The title clathrates possess very low thermal expansion coefficients ranging from 6.6 × 10(-6) to 1.0 × 10(-5) K(-1) in the temperature range of 298-1100 K. The characteristic Debye temperature is about 490 K. Measurements of the electrical resistivity and thermopower showed typical behavior of p-type thermally activated semiconductors, whereas the temperature behavior of the thermal conductivity is glasslike and in general consistent with the PGEC concept. The highest value of the thermoelectric figure of merit (ZT = 0.1) was achieved for the Br-bearing clathrate Si(32.1(2))P(13.9(2))Te(6.6(2))Br(1.0(1)) at 750 K.

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The cationic clathrate Si46−2xP2xTex crystal growth by chemical vapour transport

Cited by 18 publications

References 21 publications

Cationic Clathrate I Si_46-xP_xTe_y (6.6(1) ≤ y ≤ 7.5(1), x ≤ 2y): Crystal Structure, Homogeneity Range, and Physical Properties

Cationic Clathrate I Si_46-xP_xTe_y (6.6(1) ≤ y ≤ 7.5(1), x ≤ 2y): Crystal Structure, Homogeneity Range, and Physical Properties

Modeling of Thermodynamic Properties and Phase Equilibria of the Si-P System

Homo- and Heterovalent Substitutions in the New Clathrates I Si₃₀P₁₆Te_8–xSe_x and Si_30+xP_16–xTe_8–xBr_x: Synthesis, Crystal Structure, and Thermoelectric Properties

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The cationic clathrate Si46−2xP2xTex crystal growth by chemical vapour transport

Cited by 18 publications

References 21 publications

Cationic Clathrate I Si46-xPxTey (6.6(1) ≤ y ≤ 7.5(1), x ≤ 2y): Crystal Structure, Homogeneity Range, and Physical Properties

Cationic Clathrate I Si46-xPxTey (6.6(1) ≤ y ≤ 7.5(1), x ≤ 2y): Crystal Structure, Homogeneity Range, and Physical Properties

Modeling of Thermodynamic Properties and Phase Equilibria of the Si-P System

Homo- and Heterovalent Substitutions in the New Clathrates I Si30P16Te8–xSex and Si30+xP16–xTe8–xBrx: Synthesis, Crystal Structure, and Thermoelectric Properties

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Cationic Clathrate I Si_46-xP_xTe_y (6.6(1) ≤ y ≤ 7.5(1), x ≤ 2y): Crystal Structure, Homogeneity Range, and Physical Properties

Cationic Clathrate I Si_46-xP_xTe_y (6.6(1) ≤ y ≤ 7.5(1), x ≤ 2y): Crystal Structure, Homogeneity Range, and Physical Properties

Homo- and Heterovalent Substitutions in the New Clathrates I Si₃₀P₁₆Te_8–xSe_x and Si_30+xP_16–xTe_8–xBr_x: Synthesis, Crystal Structure, and Thermoelectric Properties