Crystal Structure of FePb 4 Sb 6 Se 14 and its Structural Relationship with FePb 3 Sb 4 Se 10

Single crystals of FePb 4 Sb 6 Se 14 , were obtained from solid‐state combination of high purity elemental powders at 873K for three days. Single crystal X‐ray structure determination revealed that the compound crystallizes in the monoclinic space group P 2 1 / c (no. 14) and adopts the structure of Jamesonite (FePb 4 Sb 6 S 14 ). The structure contains two crystallographically independent lead atoms with monocapped and bicapped trigonal prismatic coordinations, three antimony atoms located in a distorted octahedral environment and one iron atom occupying a flattened octahedral coordination. Neighboring monocapped and bicapped trigonal prims around lead atoms share faces and edges to build a corrugated layer parallel to the ac plane. Octahedrally coordinated antimony atoms share edges to form one‐dimensional (1D) {SbSe} ∞ ribbons connecting adjacent corrugated layers. The distortion of the octahedral coordination around antimony atoms within the {SbSe} ∞ ribbons with the longest bond pointing towards the center of the ribbon, suggests the stereochemical activity of antimony lone‐pairs with their electron clouds pointing towards the center of the {SbSe} ∞ ribbon. The three dimensional framework resulting from the connectivity between the corrugated layers and the {SbSe} ∞ ribbons, contains isolated cylindrical voids parallel to [100] which are filled by a 1D Fe n Se 4n+2 straight chain of edge‐sharing FeSe 6 octahedra. The crystal structure of FePb 4 Sb 6 Se 14 is closely related to that of FePb 3 Sb 4 Se 10 as they are formed by similar building units with different sizes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95198/1/2549_ftp.pd

1H and 13C NMR assignments for a series of Diels–Alder adducts of anthracene and 9‐substituted anthracenes

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111949/1/mrc4268.pd

The structures and thermoelectric properties of the infinitely adaptive series (Bi2)m(Bi2Te3)n

The structures and thermoelectric properties of the (Bi2)m(Bi2Te3)n homologous series, derived from stacking hexagonal Bi2 and Bi2Te3 blocks, are reported. The end-members of this series are metallic Bi and semiconducting Bi2Te3; nine members of the series have been studied. The structures form an infinitely adaptive series and a unified structural description based on a modulated structure approach is presented. The as-synthesized samples have thermopowers (S) that vary from n-type for Bi2Te3 to p-type for phases rich in Bi2 blocks but with some Bi2Te3 blocks present, to n-type again for Bi metal. The thermoelectric power factor (S2/rho) is highest for Bi metal (43 muW/K2 cm at 130 K), followed by Bi2Te3 (20 muW/K2 cm at 270 K), while Bi2Te (m:n = 5:2) and Bi7Te3 (m:n = 15:6) have 9 muW/K2 cm (at 240 K) and 11 muW/K2 (at 270 K), respectively. The results of doping studies with Sb and Se into Bi2Te are reported.Comment: accepted for publication in PR

4-(8-Eth­oxy-2,3-dihydro-1H-cyclo­penta­[c]quinolin-4-yl)butane-1-peroxol

In the title mol­ecule, C18H23NO3, the hydro­per­oxy­butyl substituent is nearly fully extended, with the four torsion angles in the range 170.23 (10)–178.71 (9)°. The O—O distance in the hydro­peroxide group is 1.4690 (13) Å. This group acts as an inter­molecular hydrogen-bond donor to a quinoline N atom. This results in dimeric units about the respective inversion centers, with graph-set notation R 2 2(18)

Correlation between microstructure and drastically reduced lattice thermal conductivity in bismuth telluride/bismuth nanocomposites for high thermoelectric figure of merit

The concept of nanocomposite/nanostructuring in thermoelectric materials has been proven to be an effective paradigm for optimizing the high thermoelectric performance primarily by reducing the thermal conductivity. In this work, we have studied the microstructure details of nanocomposites derived by incorporating a semi-metallic Bi nanoparticle phase in Bi2Te3 matrix and its correlation mainly with the reduction in the lattice thermal conductivity. Incorporating Hi inclusion in Bi2Te3 bulk thermoelectric material results in a substantial increase in the power factor and simultaneous reduction in the thermal conductivity. The main focus of this work is the correlation of the microstructure of the composite with the reduction in thermal conductivity. Thermal conductivity of the matrix and nanocomposites was derived from the thermal diffusivity measurements performed from room temperature to 150 degrees C. Interestingly, significant reduction in total thermal conductivity of the nanocomposite was achieved as compared to that of the matrix. A detailed analysis of high-resolution transmission electron microscope images reveals that this reduction in the thermal conductivity can be ascribed to the enhanced phonon scattering by distinct microstructure features such as interfaces, grain boundaries, edge dislocations with dipoles, and strain field domains

Chemical Manipulation of Magnetic Ordering in Mn_1–<i>x</i>Sn_<i>x</i>Bi₂Se₄ Solid–Solutions

Several compositions of manganese–tin–bismuth selenide solid–solution series, Mn_1–<i>x</i>Sn_<i>x</i>Bi₂Se₄ (<i>x</i> = 0, 0.3, 0.75), were synthesized by combining high purity elements in the desired ratio at moderate temperatures. X-ray single crystal studies of a Mn-rich composition (<i>x</i> = 0) and a Mn-poor phase (<i>x</i> = 0.75) at 100 and 300 K revealed that the compounds crystallize isostructurally in the monoclinic space group <i>C</i>2/<i>m</i> (no.12) and adopt the MnSb₂Se₄ structure type. Direct current (DC) magnetic susceptibility measurements in the temperature range from 2 to 300 K indicated that the dominant magnetic ordering within the Mn_1–<i>x</i>Sn_<i>x</i>Bi₂Se₄ solid–solutions below 50 K switches from antiferromagnetic (AFM) for MnBi₂Se₄ (<i>x</i> = 0), to ferromagnetic (FM) for Mn_0.7Sn_0.3Bi₂Se₄ (<i>x</i> = 0.3), and finally to paramagnetic (PM) for Mn_0.25Sn_0.75Bi₂Se₄ (<i>x</i> = 0.75). We show that this striking variation in the nature of magnetic ordering within the Mn_1–<i>x</i>Sn_<i>x</i>Bi₂Se₄ solid–solution series can be rationalized by taking into account: (1) changes in the distribution of magnetic centers within the structure arising from the Mn to Sn substitutions, (2) the contributions of spin-polarized free charge carriers resulting from the intermixing of Mn and Sn within the same crystallographic site, and (3) a possible long-range ordering of Mn and Sn atoms within individual {M}_<i>n</i>Se_4<i>n</i>+2 single chain leading to quasi isolated {MnSe₆} octahedra spaced by nonmagnetic {SnSe₆} octahedra

Carrier Mobility Modulation in Cu₂Se Composites Using Coherent Cu₄TiSe₄ Inclusions Leads to Enhanced Thermoelectric Performance

Carrier transport engineering in bulk semiconductors using inclusion phases often results in the deterioration of carrier mobility (μ) owing to enhanced carrier scattering at phase boundaries. Here, we show by leveraging the temperature-induced structural transition between the α-Cu2Se and β-Cu2Se polymorphs that the incorporation of Cu4TiSe4 inclusions within the Cu2Se matrix results in a gradual large drop in the carrier mobility at temperatures below 400 K (α-Cu2Se), whereas the carrier mobility remains unchanged at higher temperatures, where the β-Cu2Se polymorph dominates. The sharp discrepancy in the electronic transport within the α-Cu2Se and β-Cu2Se matrices is associated with the formation of incoherent α-Cu2Se/Cu4TiSe4 interfaces, owing to the difference in their atomic structures and lattice parameters, which results in enhanced carrier scattering. In contrast, the similarity of the Se sublattices between β-Cu2Se and Cu4TiSe4 gives rise to coherent phase boundaries and good band alignment, which promote carrier transport across the interfaces. Interestingly, the different cation arrangements in Cu4TiSe4 and β-Cu2Se contribute to enhanced phonon scattering at the interfaces, which leads to a reduction in the lattice thermal conductivity. The large reduction in the total thermal conductivity while preserving the high power factor of β-Cu2Se in the (1–x)Cu2Se/(x)Cu4TiSe4 composites results in an improved ZT of 1.2 at 850 K, with an average ZT of 0.84 (500–850 K) for the composite with x = 0.01. This work highlights the importance of structural similarity between the matrix and inclusions when designing thermoelectric materials with improved energy conversion efficiency