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Eu7Cd4Sb8-xAsx (x = 2, 3, 4, and 5) solid solutions are prepared from the elements in a molten Sn flux (alumina crucible in evacuated silica tubes, 1.

Single crystals of CeRu0.5Ni0.5Al can be obtained from a Ce-Ni melt using elements as starting materials. The presented compound crystallizes in the orthorhombic space group Pnma (no. 62) with a = 700.38(7), b = 416.92(4) and c = 1562.84(16) pm in the LaNiAl structure type. The compound shows an unusual temperature dependence of the magnetic susceptibility for T < 20 K although the cerium cations exhibit no local moment behavior. This feature is also visible in the electrical resistivity.

CaFe4As3 is a new intermetallic structure type that can be described as a framework comprising of FeAs4 tetrahedra. The structure has similarities to the 1-2-2 superconducting phase in that the Fe/As network is related to the ThCr2Si2 structure. In addition, this phase shows magnetic transitions associated with spin density waves. This phase was prepared from a Sn flux, and it has recently been reported that further expansion of this structure type via chemical substitution is limited. We have developed a solid-state synthesis route for the preparation of CaFe4As3 that involves reacting a stoichiometric combination of the constituent elements. The thermal stability of this material was investigated over the 298–1473 K temperature range. An initial investigation of the Sn grown CaFe4As3 crystals showed that residual Sn that was present on the surface of the crystals reacted with the crystals at temperatures above 1173 K to form new phases. A thermal stability study of Sn-free CaFe4As3 indicated that it decomposed to give CaFe2As2 and Fe2As. The thermal behavior of CaFe2As2 was also investigated and the data showed that it can also form CaFe4As3 at high temperatures. The solid-state synthesis route presented herein and additional solid solution studies may provide opportunities for the prepartion of materials with this structure type with improved electronic properties.

Zintl phase compounds with large unit cells and complex anionic structures such as Yb11Sb10 hold potential for being good thermoelectric materials. Single crystals of Ge-doped Yb11Sb10 were synthesized using a molten Sn-flux technique. Single crystal X-ray diffraction data were obtained and resulted in a composition of Yb11Sb9.3Ge0.5 which was verified by microprobe. Yb11Sb9.3Ge0.5 is isostructural to Ho11Ge10, crystallizing in a body-centered, tetragonal unit cell, space group I4/mmm, with Z = 4. The unit cell parameters of Yb11Sb9.3Ge0.5 are a = 11.8813(4), c = 17.1276(13) A with a volume of 2417.8(2) A3. These parameters correlate well with the structural refinement of previously published Yb11Sb10. The structure consists of 16 isolated Sb3− anions, 8 dumbbells, 2 square planar rings and 44 Yb2+ cations. The Ge, doped in at 28 % occupancy, was found to be site specific, residing on the 2 square planar rings. Single crystal X-ray diffraction is most consistent with the site that makes up the square ring being less than fully occupied. The doped compound is additionally characterized by X-ray powder diffraction, differential scanning calorimetry and thermogravimetry. High temperature (300–1200 K) thermoelectric properties show that the doped compound has extremely low thermal conductivity (10–30 mW/cmK), lower than that of Yb11Sb10. Temperature dependent resistivity is consistent with a heavily doped semiconductor. Yb11Sb9.3Ge0.5 shows p-type behavior increasing from ∼22 μV/K at room temperature to ∼31 μV/K at 1140 K. The low value and the temperature dependence of the Seebeck coefficient suggest that bipolar conduction produces a compensated Seebeck coefficient and consequently a low zT.

Ba1.9Ca2.4Mg9.7Si7 was grown as large crystals from the reaction of silicon with barium and calcium in Mg/Al flux. This compound is a charge-balanced Zintl phase with the Zr2Fe12P7 structure type in hexagonal space group P6 (a = 11.196(2) A, c = 4.4595(9) A); barium occupies the Zr sites, the lighter alkaline earths (Mg, Ca) mix on the Fe sites, and silicon occupies the phosphorus sites. An isostructural germanide (Ba1.2Sr0.9Mg11.9Ge7, a = 11.064(1) A, c = 4.3709(6) A)) was similarly synthesized from reactions of germanium with barium and strontium in Mg/Al flux. Density of states calculations indicate these phases are semimetals, in agreement with their charge-balanced nature. Measurements of electrical resistivity, thermal conductivity, and Seebeck coefficient were carried out from 300–1000 K to investigate the thermoelectric properties of Ba1.9Ca2.4Mg9.7Si7. This compound is an n-type semimetal with low thermal conductivity (2 W/(m·K)), moderate Seebeck coefficient (−200 μV/K at 900 K), and a thermoel...

Single crystals of Eu11Cd6-xZnxSb12 (0 ≤ x ≤ 6) are prepared by reaction of the elements in a Sn flux (950 °C; cooling to 650 °C with a rate of 5 °C/h).

A series of M8Ga8Si38 (M: K, Rb, Cs) compounds with type I clathrate structure and K8Al8Si38 are prepared by heating 9:8:38 molar mixtures of the alkali metal, Ga or Al, and Si.

Ba1-xKxFe2As2 (0 ≤ x ≤ 1) superconductors are prepared by high-energy ball milling of BaH2, KH, and FeAs (containing 6% FeAs2 as impurity) and subsequent annealing (Nb container in evacuated silica tubes, 773—1173 K, 2 d).

The Zintl phases Yb14MgSb11 (I) and Ca14MgSb11 (II) are prepared by annealing mixtures of the elements in the molar ratio Yb(Ca):Mg:Sb of 14:2:11 (Nb tube in evacuated silica tubes, 1275 K for (I) and 1225 K for (II)).

Si nanoparticles are prepared by reaction of the Zintl phases Na4Si4, Rb7NaSi8, and M12Si17 (M: K, Rb, Cs) with NH4Br in DMF.

Octanol capped silicon nanoparticles crystallizing in the metastable BC8 structure are prepared by a colloidal route from mixtures of SiI4, n-butyllithium, dioctylether, and 1-octanol (280 °C, 72 h, 25—35% yield).

Single crystals of the title compounds are prepared from the elements in a Sn flux (alumina crucibles, 950 °C, 96 h) and characterized by powder and single crystal XRD, transport properties measurements, and TB-LMTO-ASA electronic structure calculations.

The title compounds are prepared by solid state reaction of stoichiometric mixtures of the elements (823—1323 K, 12—96 h).

The EuBi system contains the phases Eu5Bi3, Eu4Bi3 and Eu11Bi10. The structure types of these phases have been determined by powder X-ray diffraction. Crystals of Eu4Bi3 (cubic, space group I43d; a = 9.920 A, Z = 4, T = 130 K, R1/wR2 = 4.86/10.84%) were obtained in low yield by reaction of Eu, Mn, and Bi in the ratio 14:1:11 in a closed niobium tube (heating rate 30°C/h; reaction at 1050°C for 300 h, cooling rate 100°C/h). The crystal structure consists of distorted octahedra made up of six Bi coordinated to a central Eu atom. Eu is also coordinated to a three other Eu atoms and forms a three-dimensional network composed of interconnected rings. The Bi atoms are coordinated to eight Eu atoms. High yields of Eu4Bi3 can be prepared by reacting stoichiometric amount of the elements in a sealed tantalum tube at 1100°C for 24 h. Temperature dependent magnetic susceptibility is consistent with antiferromagnetic behavior with an ordering temperature of 18 K. The data could be fit with the Curie-Weiss law and a moment of 7.38 μB/Eu is obtained, consistent with all Eu atoms being Eu11. Temperature dependent resistivity indicates that Eu4Bi3 is a metal with a room temperature resistance of 1.3 Ωcm. Eu4Bi3: Kristallstruktur, magnetische und elektronische Eigenschaften Das System EuBi enthalt die Phasen Eu5Bi3, Eu4Bi3 und Eu11Bi10. Die Strukturen dieser Phasen wurden durch Pulver-Rontgenbeugungsuntersuchungen bestimmt. Kristalle von Eu4Bi3 (kubisch, Raumgruppe I43d; a = 9,920 A, Z = 4, T = 130 K, R1/wR2 = 4,86/10,84%) wurden in geringer Ausbeute durch Reaktion von Eu, Mn und Bi im molaren Verhaltnis 14:1:11 in einer verschlossenen Niobampulle erhalten (Aufheizrate: 30°C/h; Reaktion bei 1050°C, 300 h; Abkuhlrate: 100°C/h). Die Kristallstruktur besteht aus [EuBi6]-Oktaedern, wobei Eu zu drei weiteren Eu-Atomen koordiniert ist und ein dreidimensionales Netzwerk aus miteinander verknupften Ringen bildet. Die Bi-Atome haben 8 Eu-Atome als nachste Nachbarn. Eu4Bi3 kann in hoher Ausbeute durch Umsetzung von stochiometrischen Mengen der Elemente in einer verschlossenen Tantalampulle bei 1100°C (24 h) erhalten werden. Messungen der magnetischen Suszeptibilitat in Abhangigkeit von der Temperatur zeigen antiferromagnetisches Verhalten mit einer Ordnungstemperatur von 18 K. Die Werte gehorchen dem Curie-Weiss-Gesetz mit einem magnetischen Moment von 7,38 μB/Eu, was fur zweiwertiges Europium spricht. Widerstandsmessungen in Abhangigkeit von der Temperatur zeigen, das Eu4Bi3 metallisch ist mit einem Widerstand von 1,3 Ωcm bei Raumtemperatur.

Single crystals of CeRu0.5Ni0.5Al are prepared from the elements in a molten Ce0.78Ni0.22 flux (1000 °C for 12 h and 850 °C for 48 h).

Crystals of Yb14-xCaxMnSb11 (x = 2, 4, 6, 8) solid solutions are prepared by reaction of the elements in a Sn flux (excess Mn, alumina crucible sealed in a quartz tube, 1000 °C).

Samples of Sr8AlxSi46-x existing in the narrow composition range of 9.54 ≤ x ≤ 10.30 are synthesized by arc-melting of the elements and characterized by powder XRD, electrical transport measurements, and TB-LMTO-ASA electronic structure calculations.

Single crystals of the new title compound are prepared by a molten flux method from mixtures of the elements in the atomic ratio Eu:Ga:P = 3:120:4 (alumina crucible, 1370 K, 16 h).

Na4Si4-xPx (x = 0.04, 0.08, 0.12) is prepared by reaction of Na with mechanically alloyed Si4-x/Px mixtures (Nb tube, 650 °C, 3 d).

There are a wide variety of ternary compounds, AxMyXz, where A = alkali or alkaline earth metal, M = semimetal or main group element and X = pnictide, that have been synthesized. For example the compounds Ba3AlSb3, Ca3AlSb3, Ca3AlSb3 and Ca5Al2Sb6 have been synthesized and their structures can be understood via the Zintl formalism which can be simply stated as the octet rule for all atoms. The structures can be generally formulated as A− + [(MX)−] so that the anionic units in these examples may be written as: (Al2Sb6)12-; (AlSb3)6- chains; a (Al2Sb6)10- network; and [(AlSb9- 4) + 4Sb3- + Sb7- 3). The Zintl concept has also been applied to ternary transition metal compounds such as the lanthanum transition metal pnictides and ternary transition metal chalcogenides. These structures and their related properties can be understood in terms of cations and complex polyatomic anionic units. The Zintl concept, as it applies to ternary pnictide compounds, will be presented and its extension to ternary tra...

The authors have theoretically studied the bonding properties of Ca{sub 14}GaAs{sub 11} using the ab initio, self-consistent pseudopotential method within the local density approximation of density functional theory. Ca{sub 14}GaAs{sub 11} is an example of a new series of recently prepared compounds which have the stoichiometry A{sub 14}MPn{sub 11} (A = Ca, Sr, Ba; M = Al, Ga, Mn; Pn = As, Sb, Bi). They have found that the electronic structure and bonding of the Ca{sub 14}GaAs{sub 11} compound are consistent with the Zintl concept. In addition, the GaAs{sub 4} tetrahedra and the linear As{sub 3} groups contained in this compound are isolated units which are not arranged into an extended bonding network. The bonding within the GaAs{sub 4} group is slightly more ionic than the bonding in a GaAs crystal. The linear As{sub 3} unit can be accurately described as a hypervalent three-center, four-electron bonded structure. The A{sub 14}MPn{sub 11} structure type contains the first example of a discrete, hypervalent group 15 linear anion.

A new rare earth metal Zintl compound, Eu14MnSb11, has been prepared in high yield from reacting stoichiometric amounts of the elements in a sealed tantalum tube, sealed in a quartz ampoule, at 1250 °C for 24 h. Eu14MnSb11 is isostructural with the Zintl compounds A14MPn11 (A = Ca, Sr, Ba; M = Al, Ga, Mn; Pn = As, Sb, Bi). Single crystal X-ray diffraction shows that this compound crystallizes in the tetragonal space group I4 1 /acd, a = 17.300(3) A , c = 22.746(4) A , T = 130 K , Z = 8 .

There are a number of binary compounds which can be described as valence compounds and whose structures can be rationalized using the Zintl-Klemm rule, and are therefore considered to be Zintl compounds. Although some of these binary compounds are made up of anionic partial structures that are isoelectronic and isostructural with elemental structures, there are a large number of compounds with entirely new anionic structures. Considering the large number of binary compounds that exist whose structures are known, it is surprising that there are new structures are known, it is surprising that there are new structures still waiting to be discovered. Serendipity sometimes is the key, and herein we describe the synthesis, structure, and electronic characterization of the Zintl compound KSb{sub 2}.

Layered pnictide oxides are an unusual class of compounds which have received little attention. The characteristic feature of these materials is the presence of pnictogen and oxygen atoms which are not bonded to each other and are considered to be anions. This class of compounds is made up of ternary pnictide oxides of alkaline or rare earth metals, and quaternary pnictide oxides of alkali or alkaline earth metal along with transition metals. This Comment discusses structure and bonding in this small group of compounds. Additionally, magnetic and electronic properties of many of the transition metal pnictide oxide compounds are presented.

The EuBi system contains the phases Eu5Bi3, Eu4Bi3 and Eu11Bi10. The structure types of these phases have been determined by powder X-ray diffraction. Crystals of Eu4Bi3 (cubic, space group I43d; a = 9.920 A, Z = 4, T = 130 K, R1/wR2 = 4.86/10.84%) were obtained in low yield by reaction of Eu, Mn, and Bi in the ratio 14:1:11 in a closed niobium tube (heating rate 30°C/h; reaction at 1050°C for 300 h, cooling rate 100°C/h). The crystal structure consists of distorted octahedra made up of six Bi coordinated to a central Eu atom. Eu is also coordinated to a three other Eu atoms and forms a three-dimensional network composed of interconnected rings. The Bi atoms are coordinated to eight Eu atoms. High yields of Eu4Bi3 can be prepared by reacting stoichiometric amount of the elements in a sealed tantalum tube at 1100°C for 24 h. Temperature dependent magnetic susceptibility is consistent with antiferromagnetic behavior with an ordering temperature of 18 K. The data could be fit with the Curie-Weiss law and a moment of 7.38 μB/Eu is obtained, consistent with all Eu atoms being Eu11. Temperature dependent resistivity indicates that Eu4Bi3 is a metal with a room temperature resistance of 1.3 Ωcm. Eu4Bi3: Kristallstruktur, magnetische und elektronische Eigenschaften Das System EuBi enthalt die Phasen Eu5Bi3, Eu4Bi3 und Eu11Bi10. Die Strukturen dieser Phasen wurden durch Pulver-Rontgenbeugungsuntersuchungen bestimmt. Kristalle von Eu4Bi3 (kubisch, Raumgruppe I43d; a = 9,920 A, Z = 4, T = 130 K, R1/wR2 = 4,86/10,84%) wurden in geringer Ausbeute durch Reaktion von Eu, Mn und Bi im molaren Verhaltnis 14:1:11 in einer verschlossenen Niobampulle erhalten (Aufheizrate: 30°C/h; Reaktion bei 1050°C, 300 h; Abkuhlrate: 100°C/h). Die Kristallstruktur besteht aus [EuBi6]-Oktaedern, wobei Eu zu drei weiteren Eu-Atomen koordiniert ist und ein dreidimensionales Netzwerk aus miteinander verknupften Ringen bildet. Die Bi-Atome haben 8 Eu-Atome als nachste Nachbarn. Eu4Bi3 kann in hoher Ausbeute durch Umsetzung von stochiometrischen Mengen der Elemente in einer verschlossenen Tantalampulle bei 1100°C (24 h) erhalten werden. Messungen der magnetischen Suszeptibilitat in Abhangigkeit von der Temperatur zeigen antiferromagnetisches Verhalten mit einer Ordnungstemperatur von 18 K. Die Werte gehorchen dem Curie-Weiss-Gesetz mit einem magnetischen Moment von 7,38 μB/Eu, was fur zweiwertiges Europium spricht. Widerstandsmessungen in Abhangigkeit von der Temperatur zeigen, das Eu4Bi3 metallisch ist mit einem Widerstand von 1,3 Ωcm bei Raumtemperatur.

While investigating the reported superconducting phase of Lu2Cl2C2-x, we discovered a novel synthetic route for making TaC and NbC. TaC and NbC are superconducting refractory carbides with a Tc of 10 and 12 K, respectively. TaC or NbC was initially found as impurity in reactions designed to produce Lu2Cl2C2-x. TaC and NbC can be prepared as single crystals by reacting Ta or Nb and C in a LnCl3 (Ln = Y, Lu) flux at as low of a temperature as 850 °C for 4 days. The products are characterized by powder X-ray diffraction and magnetic susceptibility. The various conditions for the preparation of the refractory carbides in rare-earth fluxes and their properties will be presented and discussed.

Europium fullerides EuxC60 (x = 1−6) were prepared by metal ammonia solution synthesis. The products were investigated by X-ray powder diffraction, optical spectroscopy, FTIR, mass spectrometry, and magnetic susceptibility. All products were amorphous by powder X-ray diffraction and were free of ammonia as determined by mass spectrometry. Products prepared with x = 1, 2, 3 showed the presence of unreacted C60 in the optical spectra, FTIR spectra, and the powder diffraction pattern. FTIR spectra of the EuxC60 prepared with x = 3 show red-shifted frequencies of F1u(4) at 1399 and 1352 (1411) cm-1, suggesting the presence of C60- and C606-. FTIR spectra of EuxC60 samples prepared with x = 4, 5, 6 also show red-shifted frequencies and are discussed in detail. Magnetic susceptibility measurements show Curie−Weiss behavior above 50 K with experimental magnetic moments of 6.6 (1), 6.9 (1), and 5.9 (1) μB/Eu for x = 3, 4, 5 samples, respectively.

Results of magnetic property measurements for the compounds A, Mn, Pn, O, (A Sr, Ba; Pn P, As, Sb) are reported and discussed in the light of structural trends in the series. The structure consists of a 1:1 intergrowth of metal oxide layers in which the metal coordination is square planar and metal pnictide layers in which the coordination is tetrahedral. With the exception of Sr 2 Mn 2 As 2 O 2 , magnetic susceptibility data reveal the presence of broad maxima that have been assigned to coupling of the MnO 2 layers. The data have been fitted assuming a 2D heisenberg antiferromagnet model and the intraplanar coupling constants obtained are observed to increase as the α parameter or metal oxygen bond length decreases. The same trend is observed for the relationship of transition temperatures, obtained from d 1 T /d T plots, to the α axial parameters. The exception to the rule is Sr 2 Mn 2 As 2 O 2 , which has an anomalously low transition temperature and different magnetic behavior for field-cooled versus zero-field-cooled samples. The field-cooled data show a sharp antiferromagnetic transition whereas the zero-field-cooled data show no transition to 3D order between 5 and 300 K.

A new barium copper phosphide compound, BaCu10P4, was synthesized by reacting stoichiometric amounts of the elements at 1200 °C for 24 h. BaCu10P4 crystallizes in the monoclinic space group C2/m, with unit cell dimensions a = 23.288(4) b = 3.9070(10), and c = 9.534(2) A and β = 92.26(2)° (Z = 4). The structure can be described as consisting of chains of edge-shared Cu4 tetrahedral prisms that are knitted together by P atoms. The structure is related to BaCu8P4, which can be described in a similar fashion. Temperature-dependent resistivity measurements indicate that BaCu10P4 is a metal. Extended Huckel band calculations are consistent with metallic character for BaCu10P4 through Cu−Cu interactions. Orbitals at the Fermi level show Cu−Cu bonding overlap. On the other hand, BaCu8P4 reveals extremely weak Cu−Cu interactions, but rather optimizes Cu−P bonding.

New rare-earth transition-metal compounds Eu14MnPn11 and Eu14InPn11 (Pn = Sb, Bi) have been prepared in quantitative yield from heating stoichiometric amounts of the elements, which are sealed in a welded tantalum tube that is enclosed in a fused silica ampule, at 950−1200 °C. These compounds are isostructural with the Zintl compound Ca14AlSb11 and crystallize in the tetragonal space group I41/acd (Z = 8). Single-crystal X-ray data (143 K) were refined for Eu14InSb11 (a = 17.280 (5) A, c = 23.129 (8) A, R1 = 4.04%, wR2 = 8.65%) and Eu14MnBi11 (a = 17.632 (4) A, c = 23.047(6) A, R1 = 4.53%, wR2 = 7.83%). The structures of these compounds are compared with Eu14MnSb11 and other compounds of this structure type. Magnetization measurements show that Eu14MnSb11 and Eu14MnBi11 order at approximately 100 and 35 K, respectively. The effective moment in the paramagnetic state for Eu14MnSb11 is μeff = 27.0(1) μB and for Eu14MnBi11 is μeff = 27.1(1) μB. Eu14MnSb11 saturates with μsat = 102 μB at 5 K whereas Eu14MnBi1...

Two rare-earth Zintl phases, Yb_(11)GaSb_9 and Yb_(11)InSb_9, were synthesized in high-temperature self-fluxes of molten Ga and In, respectively. Structures were characterized by both single-crystal X-ray diffraction and powder X-ray diffraction and are consistent with the published orthorhombic structure, with the space group Iba2. High-temperature differential scanning calorimetry (DSC) and thermal gravimetry (TG) measurements reveal thermal stability to 1300 K. Seebeck coefficient and resistivity measurements to 1000 K are consistent with the hypothesis that Yb_(11)GaSb_9 and Yb_(11)InSb_9 are small band gap semiconductors or semimetals. Low doping levels lead to bipolar conduction at high temperature, preventing a detailed analysis of the transport properties. Thermal diffusivity measurements yield particularly low lattice thermal conductivity values, less than 0.6 W/m K for both compounds. The low lattice thermal conductivity suggests that Yb_(11)MSb_9 (M = Ga, In) has the potential for high thermoelectric efficiency at high temperature if charge-carrier doping can be controlled.

HRTEM image of a single Ge nanocrystal. The image has been rotationally filtered to improve clarity. The lattice fringes imaged are for Ge 〈111〉, with a d spacing of 3.27 A. Reaction between the Zintl salt NaGe and GeCl4 is shown to produce Ge nanocrystals. The reaction proceeds readily in refluxing diglyme at ambient pressure. The nanocrystals produced may be surface-terminated by reaction with RLi or RMgBr and demonstrate quantum confinement.

We have studied the electronic properties of Zintl phase KSi, by the ab initio density functional pseudopotential method. Our interest in this Zintl compound is in its current use as a reagent in the synthesis of Si nanoclusters. The structure consists of isolated Si4 tetrahedra with K atoms situated above each face. The crystal system is cubic with the symmetry of the P43m space group. Band structure calculations show a band gap of 1.3 eV. The presence of K atoms has widened the band gap over that found between occupied and unoccupied energy levels in the Si4 cluster. The valence bandwidth lies between the valence bandwidth of crystalline Si with diamond structure and the width of the occupied energy levels of the Si4 cluster. The density of states shows four major structures for the occupied bands. The lowest energy band of conduction states is also given in the density of states plot. The nature of the bonding in the crystal is revealed by an examination of the charge density associated with each of t...

Rare-earth transition metal compounds Yb14MnSb11 and Yb14MnBi11 have been prepared by heating stoichiometric amounts of the elements at 1000−1200 °C. These compounds are isostructural with the Zintl compound Ca14AlSb11 and crystallize in the tetragonal space group I41/acd (Z = 8). Single-crystal X-ray data (143 K) were refined for Yb14MnSb11 [a = 16.615(2) A, c = 21.948(4) A, V = 6059(2) A3, and R1/wR2 (0.0299/0.0479)] and Yb14MnBi11 [a = 17.000(3) A, c = 22.259(6) A, V = 6433(2) A3, R1/wR2 (0.0631/0.133)]. Structural analysis is consistent with Yb2+. Temperature-dependent magnetic susceptibility data show that Yb14MnSb11 orders ferromagnetically at 56 K and Yb14MnBi11 has a ferromagnetic transition at 58 K and another transition at 28 K. High-temperature magnetic susceptibility data can be fit with a modified Curie−Weiss law and give μeff = 4.92(2)μB and μeff = 4.9(1)μB for the Sb and Bi compounds, respectively. This result is consistent with the assignment of Mn3+ (d4) and Yb2+ (f 14). Single-crystal ma...

A hydrogen-containing inorganic clathrate with the nominal composition, K(7)(H(2))(3)Si(46), has been prepared in 98% yield by the reaction of K(4)Si(4) with NH(4)Br. Rietveld refinement of the powder X-ray diffraction data is consistent with the clathrate type I structure. Elemental analysis and (1)H MAS NMR confirmed the presence of hydrogen in this material. Type I clathrate structure is built up from a Si framework with two types of cages where the guest species, in this case K and H(2), can reside: a large cage composed of 24 Si, in which the guest resides in the 6d position, and a smaller one composed of 20 Si, in which the guest occupies the 2a position (cubic space group Pm3n). Potassium occupancy was examined using spherical aberration (Cs) corrected scanning transmission electron microscopy (STEM). The high-angle annular dark-field (HAADF) STEM experimental and simulated images indicated that the K is deficient in both the 2a and the 6d sites. (1)H and (29)Si MAS NMR are consistent with the presence of H(2) in a restricted environment and the clathrate I structure, respectively. FTIR and (29)Si{(1)H} CP MAS NMR results show no evidence for a Si-H bond, suggesting that hydrogen is present as H(2) in interstitial sites. Thermal gravimetry (TG) mass spectrometry (MS) provide additional confirmation of H(2) with hydrogen loss at approximately 400 degrees C.

The new compounds Eu14MnAs11 and Eu14MnP11 were synthesized from stoichiometric amounts of the elements. The compounds are isotypic to Ca14AlSb11 and crystallize in the tetragonal space group I41/acd (Z = 8). Lattice parameters obtained from single-crystal X-ray diffraction at 130 K are a = 16.318 (2) A, c = 21.684 (4) A and a = 15.930 (4) A, c = 21.213 (5) A for Eu14MnAs11 and Eu14MnP11, respectively. In the refinement of each structure, the central Pn(4) site of a Pn37- linear unit (Pn = As, P) shows positional disorder; this is in contrast to the ordered structures formed when Pn = Sb and Bi. Eu14MnAs11 and Eu14MnP11 are ferromagnetic with transitions at 74 and 52 K, respectively. Eu14MnAs11 also has a low-temperature transition at ∼25 K. Resistivity measurements indicate an insulator-to-metal transition near the magnetic transition, and plots of ln ρ vs 1/T are linear above TC, providing activation energies of 0.03 eV (As; 240−300 K) and 0.31 eV (P). The resistivity is suppressed in the presence of a ...

The new pnictide oxide Sr2MnZn2As2O2 is reported. The crystal structure of this compound consists of a 1:1 intergrowth of square-planar MnO22- layers and ThCr2Si2-type Zn2As22- layers interspersed by Sr cations. This compound has been prepared by sintering the stoichiometric ratio of SrO, Mn, Zn, and As in a fused-silica ampule under 0.2 atm of Ar at 1000 °C for 1 week. The sample quality has been examined by Rietveld refinement of the powder X-ray diffraction data, and the transition metal site (2a and 4d) selectivity has been analyzed by Rietveld refinement of powder neutron diffraction data. Furthermore, effects of this structural order on the magnetic susceptibility and interaction between the magnetic layers have been analyzed by temperature-dependent magnetization measurements. The magnetic structures of both phases, A2MnZn2As2O2 (A = Sr, Ba), have been investigated by temperature-dependent powder neutron diffraction. The Ba analogue exhibits two-dimensional short-range order below about 40 K, where...