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The flexible metal organic framework (MOF) compound, Ni(L)[Ni(CN)4], (L = 4,4′azopyridine (C10N4H8), nicknamed AzoPyr) is a 3D porous material that adopts the Hofmann-type structure. This paper reports our synthesis of Ni-AzoPyr and its structural, bonding, and sorption characterization. The red monoclinic crystals (with space group P2/n) were found to be multiple twins with three main components related by twin laws. The lattice parameters are a = 7.102 (3) A, b = 14.154 (4) A, c = 25.655 (10) A, β = 92.575 (12)°, and V = 2577 (2) A3. Ni-AzoPyr adopts a pillared structure with layers defined by the 2-D Ni [Ni(CN)4]n nets and AzoPyr ligands as pillars linking between 6-fold coordinated Ni3 sites. An additional AzoPyr ligand was found to cross link between the 6-fold Ni1 sites to the open ends of the four-fold Ni2 sites. This arrangement results in a 5-fold pseudo square-pyramid for Ni2 and a significantly long Ni2–N distance of 2.436 (11) A. Density functional theory (DFT) calculations show that almost all states in the conduction band minimum (CBM) are occupied by the 6-fold coordinated Ni site, indicating little to no electrons are conducted at the 5-fold coordinated Ni site. Water molecules were found to be entrapped in the cavities of the structure. In addition to the gating adsorption feature of Ni-AzoPyr, using computational approach, we found that in the absence of water molecules, the pores were found to have a local diameter of 5.8 A with a maximum number of 15.5 CO2 molecules per unit cell. The inclusion of disordered water solvent molecules gives rise to the formula of Ni(AzoPyr)[Ni(CN)4]·0.8H2O, or C19H12N10Ni2·0.8(H2O).

The crystal structure and powder patterns were prepared for the distorted perovskite series R(Co3/4Ti1/4)O3 (R = La, Pr, Nd, Sm, Eu, Gd, Dy, Ho). The R(Co3/4Ti1/4)O3 members are isostructural with each other and are crystallized in the orthorhombic crystal system with space group Pnma, Z = 4. From R = La to Ho, the lattice parameters a range from 5.4614(3) to 5.5368(2) Å, b range from 7.7442(4) to 7.4859(2) Å, and c range from 5.5046(3) to 5.2170(2) Å. The unit-cell volumes, V which range from 232.81(2) to 216.237(11) Å3 follow the trend of “lanthanide contraction”. The structure distortion of these compounds is evidenced in the tilt angles θ, ϕ, and ω, which represent rotations of an octahedron about the pseudo-cubic perovskite [110]p, [001]p and [111]p axes. All three tilt angles increase across the lanthanide series (for R = La to R = Ho: θ increases from 8.34° to 17.00°, ϕ from 6.24° to 8.53°, and ω from 10.41° to 18.96°), indicating a greater octahedral distortion as the ionic radius of R3+ [r(R3+)] decreases. The bond valence sum values for the (Co/Ti) site and the R site of R(Co3/4Ti1/4)O3 reveal no significant bond strain in these compounds. X-ray diffraction patterns of the R(Co3/4Ti1/4)O3 samples were submitted to the Powder Diffraction File.

The crystal structures, solid solution limit, and powder X-ray reference diffraction patterns for two ‘natural superlattice’ series Bi1-xBaxCuOSe (x = 0.05, 0.075, 0.1, 0.2, and 0.3), and Bi1-xCaxCuOSe (x = 0, 0.05, 0.075, 0.1, 0.2 and 0.3) have been determined. The structure/property relationships of these thermoelectric materials are summarized. As the ionic radius of Ba2+ is greater than that of Bi3+, the unit cell volume, V, of Bi1-xBaxCuOSe increases progressively from x = 0 to x = 0.2 (from 137.868 (5) A3 to 141.194 (10) A3, respectively). However, even though the ionic radius of Ca2+ is smaller than that of Bi3+, the unit cell volumes, V, of Bi1-xCaxCuOSe also show an increasing trend as a function of x (137.868 (5) A3 to 139.295 (12) A3 from x = 0 to 0.3, respectively) due to the relatively large increase in c parameter. The structure of Bi1-xAxCuOSe (A = Ba and Ca) can be considered as built from [Bi2(1-x)A2xO2]2(1−x)+ layers normal to the c-axis alternating with fluorite-like [Cu2Se2]2(1−x)- layers in the c-direction. The substitutions of Ba and Ca on the Bi site of Bi1-xAxCuOSe lead to the weakening of the ‘bonding’ between the [Bi2(1-x)A2xO2]2(1−x)+ and the [Cu2Se2]2(1−x)- layers (a decrease of Columbic force), resulting in an increase of the c-axis parameter and V. Powder X-ray diffraction patterns of Bi1-xAxCuOSe were submitted for inclusion in the Powder Diffraction File (PDF).

Crystal structures and X-ray reference powder diffraction patterns have been determined for the Ba12Nb8-xTaxCo4O36 (x = 1, 3, 4, 5, 7) series. Ba12Nb8-xTaxCo4O36 crystallize in the cubic perovskite structure with a space group Pm 3 ¯ m (No. 221) and the lattice parameter increasing from a = 4.08732(3) A to a = 4.08894 (2) A as x varies from 1 to 7. The Goldschmidt distortion parameter for the entire series is about 1.05 (1.0488–1.0506), being similar to that of the cubic end member Ba3Nb2CoO9. Transmission electron microscopy of the composition Ba12Nb4Ta4Co4O36 (or Ba3(NbTaCo)O9) revealed nanoscale 1:2 ordering of Nb/Ta and Co, manifested in the presence of the diffuse superlattice reflections. As this ordering is limited to short range, the average structures were still refined assuming the ideal-perovskite cubic symmetry. X-ray powder diffraction patterns of the studied compounds have been submitted to the Powder Diffraction File (PDF).

A combinatorial film of the LaCo1-xCrxO3 system was fabricated using the LaCoO3 and LaCrO3 targets at the NIST Pulsed Laser Deposition (PLD) facility. As the ionic size of Cr3+ is greater than that of Co3+, the unit cell volume of the series increases with increasing x. Using a custom screening tool, the Seebeck coefficient of LaCo1-xCrxO3 approaches a measured maximum of 286 μV/K, near to the cobalt-rich end of the film library (with x ≈ 0.49). The resistivity value increases continuously with increasing x. The measured power factor, PF, of this series, which is related to the efficiency of energy conversion, also exhibits a maximum at the composition of x ≈ 0.49, which corresponds to the maximum value of the Seebeck coefficient. Our results illustrate the efficiency of applying the high-throughput combinatorial technique to study thermoelectric materials.

This paper reports on the structural basis of CO2 adsorption in a representative model of flexible metal-organic framework (MOF) material, Ni(1,2-bis(4-pyridyl)ethylene)[Ni(CN)4] (NiBpene or PICNIC-60). NiBpene exhibits a CO2 sorption isotherm with characteristic hysteresis and features on the desorption branch that can be associated with discrete structural changes. Various gas adsorption effects on the structure are demonstrated for CO2 with respect to N2, CH4 and H2 under static and flowing gas pressure conditions. For this complex material, a combination of crystal structure determination and density functional theory (DFT) is needed to make any real progress in explaining the observed structural transitions during adsorption/desorption. Possible enhancements of CO2 gas adsorption under supercritical pressure conditions are considered, together with the implications for future exploitation. In situ operando small-angle neutron and X-ray scattering, neutron diffraction and X-ray diffraction under relevant gas pressure and flow conditions are discussed with respect to previous studies, including ex situ, a priori single-crystal X-ray diffraction structure determination. The results show how this flexible MOF material responds structurally during CO2 adsorption, single or dual gas flow results for structural change remain similar to the static (Sieverts) adsorption case, and supercritical CO2 adsorption results in enhanced gas uptake. Insights are drawn for this representative flexible MOF with implications for future flexible MOF sorbent design.

Acetone extraction of crystalline Ni(CN)4-based metal organic framework Ni(3-Methy-4,4′-bipyridine)[Ni(CN)4] which has dimethyl sulfoxide “DMSO” as guest molecules (nicknamed Ni-BpyMe(D) followed by evacuation yielded the guest-free crystalline framework, (Ni-BpyMe(A)). Ni-BpyMe(A) was determined to be orthorhombic, Pmma, a = 12.6025(4) A, b = 7.3324(3) A, c = 11.3095(4) A, V = 1045.07 (2) A3 and Z = 2. The structure of Ni-BpyMe(A) consists of a 3-D net built from extended 2-D [Ni(CN)4] groups. These layers are connected to each other via the BpyMe ligands at the six-fold coordinated Ni1 site while Ni2 has a four-fold coordination environment. While forming infinite square nets, the [Ni(CN)4] chains progress in a zig-zag fashion along the ab-direction; they can be projected along a or b directions. Another feature of this structure is that instead of locating the –CH3 group in one position of the pyridine ring as expected, it appears to be in two mirror-related positions on the same pyridine ring. The structure represents an average of two configurations which gives rise to the pseudosymmetry. The methyl group is distributed equally among each side of the pyridine ring; therefore, the occupancy of the methyl group is 50%. The compound exhibits a Type-I sorption characteristic. The absence of a hysteresis loop indicates that it is not likely a flexible MOF. A comparison of the structure of Ni-BpyMe(A) with the previously reported structure of Ni-BpyMe(D) with DMSO as guest molecules revealed a different structure (Monoclinic P2/n) as a result of significant increase in the bipyridyl dihedral angle from 34.87° to 90.00° after removal of the guest molecules in the pores. The change in ring orientation of the BpyMe ligands stabilize the pore structure against collapse. The structural change is relevant to gate opening behaviors observed in other MOFs although no gating behavior was indicated in the gas adsorption behavior.

X-ray reference powder patterns and structures have been determined for a series of cobalt-, nickel- and zinc-containing niobates, Co(NixZn1−x)Nb4O12(x= 0.2, 0.4, 0.6, 0.8). The Co(NixZn1−x)Nb4O12series crystallize in the space group ofPbcn, which is of the disordered columbite-type structure (α-PbO2). The lattice parameters range froma= 14.11190(13) to 14.1569(3) Å,b= 5.69965(6) to 5.71209(13) Å,c= 5.03332(5) to 5.03673(11) Å, andV= 404.844(8) to 407.296(17) Å3fromx= 0.8 to 0.2, respectively. Co(NixZn1−x)Nb4O12contains double zig-zag chains of NbO6octahedra and single chain of (Ni,Zn,Co)O6octahedra run parallel to thebc-plane. Within the same chain the NbO6octahedra share edges, while the adjacent NbO6chains are joined to each other through common oxygen corners. These double NbO6chains are further linked together along the [100]-direction through another (Co,Ni,Zn)O6units, via common oxygen corners. The edge-sharing (Co,Ni,Zn)O6also forms zig-zag chains along thec-axis. Powder X-ray diffraction patterns of this series of compounds have been submitted to be included in the Powder Diffraction File.

The structure of a series of lanthanide iron cobalt perovskite oxides, R(Fe0.5Co0.5)O3 (R = Pr, Nd, Sm, Eu, and Gd), have been investigated. The space group of these compounds was confirmed to be orthorhombic Pnma (No. 62), Z = 4. From Pr to Gd, the lattice parameter a varies from 5.466 35(13) Å to 5.507 10(13) Å, b from 7.7018(2) to 7.561 75(13) Å, c from 5.443 38(10) to 5.292 00(8) Å, and unit-cell volume V from 229.170(9) Å3 to 220.376(9) Å3, respectively. While the trend of V follows the trend of the lanthanide contraction, the lattice parameter “a” increases as the ionic radius r(R3+) decreases. X-ray diffraction (XRD) and transmission electron microscopy confirm that Fe and Co are disordered over the octahedral sites. The structure distortion of these compounds is evidenced in the tilt angles θ, ϕ, and ω, which represent rotations of an octahedron about the pseudocubic perovskite [110]p, [001]p, and [111]p axes. All three tilt angles increase across the lanthanide series (for R = Pr to R = Gd: θ increases from 12.3° to 15.2°, ϕ from 7.5° to 15.8°, and ω from 14.4° to 21.7°), indicating a greater octahedral distortion as r(R3+) decreases. The bond valence sum for the sixfold (Fe/Co) site and the eightfold R site of R(Fe0.5Co0.5)O3 reveal no significant bond strain. Density Functional Theory calculations for Pr(Fe0.5Co0.5)O3 support the disorder of Fe and Co and suggest that this compound to be a narrow band gap semiconductor. XRD patterns of the R(Fe0.5Co0.5)O3 samples were submitted to the Powder Diffraction File.

Two-dimensional transition metal dichalcogenides (2D-TMDs) are of broadening research interest due to their novel physical, electrical, and thermoelectric properties. Having the chemical formula MX 2, where M is a transition metal and X is a chalcogen, there are many possible combinations to consider for materials-by-design exploration. By identifying novel compositions and utilizing the lower dimensionality, which allows for improved thermoelectric performance (e.g., increased Seebeck coefficients without sacrificing electron concentration), MX 2 materials are promising candidates for thermoelectric applications. However, to develop these materials into wide-scale use, it is crucial to comprehensively understand the compositional affects. This work investigates the structure, electronic, and phonon properties of 18 different MX 2 materials compositions as a benchmark to explore the impact of various elements. There is significant correlation between properties of constituent transition metals (atomic mass and radius) and the structure/properties of the corresponding 2D-TMDs. As the mass of M increases, the n-type power factor and phonon frequency gap increases. Similarly, increases in the radius of M lead to increased layer thickness and Seebeck coefficient S. Our results identify key factors to optimize MX 2 compositions for desired performance.

The CaO-½Eu 2 O 3 -CoO z system prepared at 885 °C in air consists of two calcium cobaltate compounds, namely, the 2D thermoelectric oxide solid solution, (Ca 3−x Eu x )Co 4 O 9−z (0 ≤ x ≤ 0.5) which has a misfit layered structure, and the 1D Ca 3 Co 2 O 6 compound which consists of chains of alternating CoO 6 trigonal prisms and CoO 6 octahedra. Ca 3 Co 2 O 6 was found to be a point compound without the substitution of Eu on the Ca site when prepared at 885 °C. A solid solution region of distorted perovskite, (Eu 1−x Ca x )CoO 3−z (0 ≤ x ≤ 0.22, space group Pnma ) was established. The (Eu 0.91(1) Ca 0.09(1) )CoO 3−z perovskite member has a distorted structure with tilt angles θ (17.37°), ϕ (8.20°), and ω (19.16°) which represent rotations of an octahedron about the pseudo-cubic perovskite [110] p , [001] p and [111] p axes. The reported Eu 2 CoO 4 phase was not observed at 885 °C, but a ternary Ca-doped oxide, (Eu 1+x Ca 1−x )CoO 4−z ( Bmab ) where 0 ≤ x ≤ 0.10 was found to be stable at this temperature. In the peripheral binary systems, Eu was not present in the Ca site of CaO, while a small solid solution region was identified for (Eu 1−x Ca x )O (3−z)/2 (0 ≤ x ≤ 0.05). Seven solid solution tie-line regions and six three-phase regions were determined in the CaO-½Eu 2 O 3 -CoO z system in air.

The structures and powder X-ray reference diffraction patterns of the “natural superlattice” series Bi1−xPbxOCuSe (x = 0, 0.02, 0.04, 0.06, 0.08, and 0.10) have been investigated. As the ionic radius of Pb2+ is greater than that of Bi3+, the unit-cell volume of Bi1−xPbxOCuSe increases progressively from x = 0 to 0.1, namely, from 137.868(5) to 139.172(11) Å3, as expected. The structure of Bi1−xPbxOCuSe is built from [Bi2(1−x)Pb2xO2]2(1−x)+ layers normal to the c-axis alternating with [Cu2Se2]2(1−x)− fluorite-like layers. Pb substitution in the Bi site of Bi1−xPbxOCuSe leads to the weakening of the “bonding” between the [Bi2(1−x)Pb2xO2]2(1−x)+ and the [Cu2Se2]2(1−x)− layers. Powder patterns of Bi1−xPbxOCuSe were submitted to be included in the Powder Diffraction File.

X-ray data of a powder sample of α-chlorohemin (a member of the porphyrin family), C34H32ClFeN4O4, was collected using synchrotron radiation at the Advanced Photon Source (APS, Argonne National Laboratory). Rietveld Refinement and Density Functional Theory (DFT) calculations were performed for obtaining the structure including positions of hydrogen atoms. The structure was found to be P 1 ¯ , Z = 2; at 100K the lattice parameters are a = 11.22468(6) A, b = 13.93930(8) A, c = 10.79818(9) A, α = 99.6672(6)°, β = 108.4124(8)°, γ = 106.7175(6)°, and V = 1471.713(19) A3, and at 295K, a = 11.43217(7) A, b = 14.06412(10) A, c = 10.85390(9) A, α = 98.6655(7)°, β = 108.6294(8)°, γ = 107.5025(7)°, and V = 1517.21(2) A3, Dx = 1.427 g/cm3. Experimental reference X-ray patterns have also been determined, which will be included in the Powder Diffraction File (PDF).

The chartreuse monoclinic Ni-dpbz (Ni(L)[Ni(CN) 4 ], (L = 1,4-Bis(4-pyridyl)benzene, or dpbz) crystal assumes a pillared structure with layers defined by 2-D Ni[Ni(CN) 4 ] n nets and dpbz ligands as pillars, linking between coordinated Ni sites. In addition to the hysteretic adsorption/desorption feature of Ni-dpbz, in half of the parallelepiped-shape space enclosed by the pillars and nets, an additional dpbz ligand was found to link between the open ends of two four-fold Ni sites. This arrangement results in an unusual 5-fold pseudo square-pyramid environment for Ni and a significantly long Ni–N distance of 2.369(4) A. The presence of disordered dimethyl sulfoxide (DMSO) solvent molecules give rise to the formula of Ni(dpbz)[Ni(CN) 4 ]·½dpbz·0.44DMSO. Sorption isotherms showed flexible behavior during the adsorption and desorption of CO 2 .

Ambient-temperature capture of CO2 by the metal-organic framework Cu3(BTC)2 (BTC ≡ 1,3,5-benzenetricarboxylate), known as HKUST-1, has been studied in situ in a laboratory X-ray powder diffractometer under gas-flowing conditions. The diffraction patterns were collected at partial pressures of CO2 ( p C O 2 ) ranging from 0.2 bar to 6 bar. Rietveld refinements combined with the difference Fourier maps identified two principal absorption sites, which agreed with the results of previous low-temperature neutron diffraction studies. At ambient temperature, the CO2 molecules on both sites exhibit considerable positional and rotational disorder, which contrasts with their ordered positions determined by neutron diffraction at cryogenic temperatures. The amount of the adsorbed CO2 increased continuously with increasing p C O 2 and reached ≈1.8 CO2 molecules per Cu atom at p C O 2 = 6 bar. The results of this work, while providing new insights into the CO2 adsorption of HKUST-1, demonstrate that laboratory X-ray powder diffraction can be successfully used to identify locations of CO2 molecules during in situ gas-adsorption experiments.

The CaO-½Gd2O3-CoOz system prepared at 885 °C in air consists of two thermoelectric calcium cobaltate compounds, namely, the 2D thermoelectric oxide solid solution, (Ca3-xGdx)Co4O9-z (0 ≤ x ≤ 0.42) which has a misfit layered structure, and the 1D Ca3Co2O6 compound which consists of chains of alternating CoO6 trigonal prisms and CoO6 octahedra. Ca3Co2O6 was found to be a point compound. In the peripheral binary systems, Gd was not present in the Ca site of CaO, while a small solid solution region was identified for (Gd1-xCax)O(3-z)/2 (0 ≤ x ≤ 0.075). A solid solution region of distorted perovskite, (Gd1-xCax)CoO3-z (0 ≤ x ≤ 0.24, space group Pnma) was established. The structure of a member of the solid solution, (Gd0.92Ca0.08)CoO3-z, was determined using high resolution synchrotron radiation. A ternary oxide compound CaGdCoO4-z which has an orthorhombic structure (Bmab) was found to be stable at this temperature. Five solid solution tie-line regions and six three-phase regions were determined in the CaO-½Gd2O3-CoOz system. A comparison of the phase diagrams of the CaO-½R2O3-CoOz (R = La, Sm and Gd) systems is provided.

Results are presented that explore the dynamic structural changes occurring in two highly flexible nanocrystalline metal-organic framework (MOF) compounds during the adsorption and desorption of pure gases and binary mixtures. The Ni(1,2-bis(4-pyridyl)ethylene)[Ni(CN)4] and catena-bis(dibenzoylmethanato)-(4,4′-bipyridyl)nickel(II) chosen for this study are 3-D and 1-D porous coordination polymers (PCP) with a similar gate opening pressure response for CO2 isotherms at 303 K, but with differing degrees of flexibility for structural change to accommodate guest molecules. As such, they serve as a potential model system for evaluating the complex kinetics associated with dynamic structure changes occurring in response to gas adsorption in flexible MOF systems. Insights into the crystallographic changes occurring as the MOF pore structure expands and contracts in response to interactions with CO2, N2, and CO2/N2 mixtures have been obtained from in situ small-angle neutron scattering and neutron diffraction, combined with ex situ X-ray diffraction structure measurements. The role of structure in carbon capture functionality is discussed with reference to the ongoing characterization challenges and a possible materials-by-design approach.

X-ray reference powder patterns and crystal structures have been determined for a series of titanium- and cobalt-containing layered alkaline-earth compounds with nominal formula (BaxSr1−x)Ti6Co6O19(x= 0.2, 0.4, 0.6, 0.8). Structural isomorphism of the title compounds with the hexagonal ferrite BaFe12O19and magnetoplumbite (PbFe12O19), was confirmed. The (BaxSr1−x)Ti6Co6O19series crystallize in the space group ofP63/mmc(No. 194) andZ= 2. The lattice parameters range froma= 5.90729(6) Å,c= 23.2378(3) Å, andV= 702.27(2) Å3forx= 0.2 toa= 5.914 93(9),c= 23.3391(5) Å, andV= 707.15(2) Å3withx= 0.8. The structure consists of alternating spinel S-block and R-blocks. The tetrahedral sites within the spinel S-blocks are occupied with only Co2+, while Ti4+is mainly located in the octahedral sites of the spinel S-blocks and in the face-sharing octahedral site of the R-blocks. A bipyramidal mixed Co/Ti site was confirmed in the R-block of the structure. Powder X-ray diffraction patterns of this series of compounds have been submitted to be included in the Powder Diffraction File.

X-ray structural characterization and X-ray reference powder patterns have been determined for two series of iron- and cobalt-containing layered compounds (BaxSr1−x)2Co2Fe12O22 (x = 0.2, 0.4, 0.6, 0.8) and (BaxSr1−x)Co2Fe16O27 (x = 0.2, 0.4, 0.6, 0.8). The (BaxSr1−x)2Co2Fe12O22 series of compounds crystallized in the space group R$\bar 3$m (No. 166), with Z = 3. The structure is essentially that of the Y-type hexagonal ferrite, BaM2+Fe63+O11. The lattice parameters range from a = 5.859 15(8) to 5.843 72(8) Å, and c = 43.4975(9) to 43.3516(9) Å for x = 0.2 to 0.8, respectively. The (BaxSr1−x)Co2Fe16O27 series (W-type hexagonal ferrite) crystallized in the space group P63/mmc (No. 194) and Z = 2. The lattice parameters range from a = 5.902 05(12) to 5.8979(2) Å and c = 32.9002(10) to 32.8110(13) Å for x = 0.2 to 0.8. Results of measurements of the Seebeck coefficient and resistivity of these two sets of samples indicated that they are insulators. Powder X-ray diffraction patterns of these two series of compounds have been submitted to be included in the Powder Diffraction File.

Comparative measurements of the Seebeck coefficient are challenging due to the diversity of instrumentation and measurement protocols. With the implementation of standardized measurement protocols and the use of Standard Reference Materials (SRMs®), for example, the recently certified National Institute of Standards and Technology (NIST) SRM® 3451 ‘‘Low Temperature Seebeck Coefficient Standard (10–390 K)’’, researchers can reliably analyze and compare data, both intra- and inter-laboratory, thereby accelerating the development of more efficient thermoelectric materials and devices. We present a comparative overview of commonly adopted Seebeck coefficient measurement practices. First, we examine the influence of asynchronous temporal and spatial measurement of electric potential and temperature. Temporal asynchronicity introduces error in the absolute Seebeck coefficient of the order of ≈10%, whereas spatial asynchronicity introduces error of the order of a few percent. Second, we examine the influence of poor thermal contact between the measurement probes and the sample. This is especially critical at high temperature, wherein the prevalent mode of measuring surface temperature is facilitated by pressure contact. Each topic will include the comparison of data measured using different measurement techniques and using different probe arrangements. We demonstrate that the probe arrangement is the primary limit to high accuracy, wherein the Seebeck coefficients measured by the 2-probe arrangement and those measured by the 4-probe arrangement diverge with the increase in temperature, approaching ≈14% at 900 K. Using these analyses, we provide recommended measurement protocols to guide members of the thermoelectric materials community in performing more accurate measurements and in evaluating more comprehensive uncertainty limits.

A suite of complementary high-throughput screening systems for combinatorial films was developed at National Institute of Standards and Technology to facilitate the search for efficient thermoelectric materials. These custom-designed capabilities include a facility for combinatorial thin film synthesis and a suite of tools for screening the Seebeck coefficient, electrical resistance (electrical resistivity), and thermal effusivity (thermal conductivity) of these films. The Seebeck coefficient and resistance are measured via custom-built automated apparatus at both ambient and high temperatures. Thermal effusivity is measured using a frequency domain thermoreflectance technique. This paper will discuss applications using these tools on representative thermoelectric materials, including combinatorial composition-spread films, conventional films, single crystals, and ribbons.

The graphitic carbon nitride (g-C3N4) which is a two-dimensional conjugated polymer has drawn broad interdisciplinary attention as a low-cost, metal-free, and visible-light-responsive photocatalyst in the area of environmental remediation. The g-C3N4-based materials have excellent electronic band structures, electron-rich properties, basic surface functionalities, high physicochemical stabilities and are “earth-abundant.” This review summarizes the latest progress related to the design and construction of g-C3N4-based materials and their applications including catalysis, sensing, imaging, and white-light-emitting diodes. An outlook on possible further developments in g-C3N4-based research for emerging properties and applications is also included.

The increased research and development of thermoelectric materials for energy conversion applications is driven primarily by the need for improved efficiency in the global utilization of energy resources. To facilitate the search for higher efficiency thermoelectric materials, we have developed a suite of complimentary high-throughput screening systems for performing thermoelectric metrology on combinatorial thin films. These custom capabilities include a facility for combinatorial thin film synthesis and suite of tools for screening the Seebeck coefficient, electrical resistance, and thermal conductivity of combinatorial films. The room temperature Seebeck coefficient and resistance are measured via an automated multiprobe apparatus, thus obtaining the power factor, S2σ (where S = Seebeck coefficient, σ = electrical conductivity). In addition, we are developing a high temperature (>300 K) power factor screening tool. Thermal effusivity (to calculate the thermal conductivity) is measured using a frequency...

The structures and thermoelectric properties of the double-filled (Ca{sub x}Ce{sub 1−x})Fe{sub 4}Sb{sub 12} series (x=0, 0.25, 0.5, 0.75, and 1) have been studied using a combined experimental and computational methods. Compounds of (Ca{sub x}Ce{sub 1−x})Fe{sub 4}Sb{sub 12} were obtained only for x=0, 0.5, and 1. Composition with x=0.25 was found to be a mixture of x=0 and 0.5 compounds, and composition with x=0.75 was found to be a mixture of x=1 and 0.5 compounds, respectively. Our conclusions on phase formation are supported by density functional theory (DFT) calculations. In Ca{sub 0.5}Ce{sub 0.5}Fe{sub 4}Sb{sub 12,} Ca substitution in the Ce site of CeFe{sub 4}Sb{sub 12} leads to high hole concentrations, resulting in stronger semimetal transport as compared to CeFe{sub 4}Sb{sub 12}. Ca{sub 0.5}Ce{sub 0.5}Fe{sub 4}Sb{sub 12} yields a slightly higher ZT value than that of CeFe{sub 4}Sb{sub 12}, which is attributed to its lower lattice thermal conductivity. Phonon mode calculations adopting a three-particle bending model suggest that thermal conductivity is reduced upon Ca substitution because of an additional vibration mode which involves both Ca and Ce atoms. - Graphical abstract: Detailed structural information to correlate with thermoelectric properties in a series of double-filled (Ca{sub x}Ce{sub 1−x})Fe{sub 4}Sb{sub 12} skutterudite samples weremore » obtained using synchrotron X-ray diffraction and first principle calculations. - Highlights: • Research focus on phase stability of CaCe double-filled p-type skutterudite. • Stable structure forms for an equiatomic occupancy of the voids by Ca and Ce. • Samples feature two-phase mixtures with variations of filling atoms ratio. • Phase stablility is investigated by DFT total energy calculations. • Sample with Equiatomic occupancy of Ca and Ce show higher ZT.« less

The X-ray diffraction powder patterns were prepared and the crystal structures were refined for the double-perovskite series of compounds, Sr2RSbO6 (R = Pr, Nd, Sm, Eu, Gd, Dy, Ho, Y, Er, Tm, Yb, and Lu). We found the structures of the entire Sr2RSbO6 series to be monoclinic with space group P21/n (no. 14), and Z = 2. From R = Lu to Pr, the lattice parameters “a” range from 5.7779(2) to 5.879 05(8) Å, “b” range from 5.7888(2) to 5.969 52(9) Å, “c” range from 8.1767(3) to 8.369 20(12) Å, “β” range from 90.112(2)° to 90.313(1)°, and “V” range from 273.483(4) to 293.714(7) Å3. These lattice parameters follow the well-established trend of “lanthanide contraction”. The R3+ and Sb5+ ions are found to be fully ordered in the double-perovskite arrangement of alternating corner-sharing octahedra in a zigzag fashion. The SrO12, RO6, and SbO6 cages are all found to have distorted coordination environments. Powder diffraction patterns of these compounds have been prepared, submitted, and published in the Powder Diffraction File.

The crystal structure and powder X-ray diffraction (XRD) patterns for three skutterudite samples, Fe(Sb2+xTe1−x),x = 0.05, 0.10, 0.20, have been determined. These compounds crystallize in the cubic space group$Im\bar 3$. Te was found to randomly substitute in the Sb site. Because of the fact the covalent radius of Sb is greater than that of Te, a trend of increasing lattice parameter has been observed as thexvalue in Fe(Sb2+xTe1−x) increases [cell parameters range from 9.10432(4) to 9.11120(3) Å forx = 0.0 to 0.2, respectively]. The Fe–Sb/Te bond distance also increases progressively [from 2.5358(4) to 2.5388(4) Å] as the Te content decreases. While average Sb/Te–Sb/Te distances in the four-membered rings are similar in these three compounds, the average Sb/Te–Sb/Te edge distances in the octahedral framework increase progressively from 3.5845(12) to 3.5900(13) Å. Reference XRD patterns of these three phases have been prepared to be included in the Powder Diffraction File (PDF).

FeSb2Te, a ternary derivative of binary CoSb3, displays anomalous electrical and thermal transport properties because of considerable modifications in the band structure induced by Fe and significant mixed valence state (namely Fe2+ and Fe3+) scattering of phonons. The substitution of Te for Sb generates more holes without notably affecting the band structure, while markedly improving the electrical conductivity and retaining a high Seebeck coefficient due to the enhanced density of states, thereby leading to dramatically increased power factors. Furthermore, the heat carrying phonons are strongly scattered with increasing x value because of the formation of solid solutions between two end members: □FeSb2Te and □FeSb3 (where □ can be viewed as a vacancy). Consequently, high thermoelectric figures of merit were achieved in the FeSb2+xTe1−x compounds, with the largest ZT value reaching ∼0.65 for the sample with x = 0.2. This is the highest value among all p-type unfilled skutterudites and is comparable with some filled compositions. Prospects for further improving the performance of p-type FeSb2Te-based skutterudites are discussed.

A critical challenge in developing engineered materials for low-energy-cost carbon capture and storage applications is to fundamentally understand adsorption, particularly when the materials exhibit hysteretic sorption behavior. We used first-principles calculations and combined with experiments to explore CO2 sorption in a nanoporous solid: cryptomelane-type manganese dioxide (OMS-2). Cations present in this material to not only stabilize its porous structure but also tailor CO2-pore interaction. The concentration, type and charge of cations have significant effects on CO2 adsorption, diffusion and hysteresis behavior. OMS-2 with lower-charge cation, e.g. K+ (Cryptomelane), exhibits less hysteresis than OMS-2 with higher-charge cation, e.g. Ba2+ (Hollandite).

The crystal structure of dehydrated NaY zeolite (Na-FAU structure type) with and without adsorbed CO 2 has been determined at 4 K and at room temperature (RT) using neutron powder diffraction techniques. The CO 2 -containing sample was prepared at 195 K and 0.1 MPa p CO2 (dry ice sublimation conditions). Neutron diffraction data provides direct evidence that adsorption of CO 2 results in significant migration of the extraframework Na cations in the zeolite structure. At 4 K, 45 of the apparent 76 CO 2 /cell were located in two crystallographically independent sites bonding to the Na cations (Na10) in the supercage site II. While the CO 2 molecule in the first site has a linear configuration interacting with Na10 via one terminal oxygen, the CO 2 molecule in the second site appears to have a bent O–C–O configuration (148.3(3)°), with both oxygen atoms coordinating to two symmetry-related Na10. Using DFT total energy calculations we found that the Na–CO 2 interaction slightly facilitates the bending motion for CO 2 by decreasing the energy cost for the 148.3(3)° bond angle by ≈0.2 eV/CO 2 . However, this Na–CO 2 interaction is not enough to cause a 32° bond angle distortion in CO 2 (the energy cost of ≈0.66 eV/CO 2 ). We propose that rotational disorder plays a significant role in the appearance of the bent CO 2 , while a small bending is possible. Our studies will help to provide a basis for interpreting CO 2 adsorption phenomena in NaY and related zeolites.

The structure and X-ray patterns of two series of barium lanthanide cobaltates, namely, Ba4Sr2R2Co4O15 (R = La, Nd, Sm, Eu, Gd, and Dy), and Ba5SrR2Co4O15 (R = La, Nd, Sm, Eu, and Gd) have been determined. These compounds crystallize in the space group P63mc; the unit-cell parameters of Ba4Sr2R2Co4O15 (R from La to Dy) decrease from a = 11.6128(2) Å to 11. 5266(9) Å, c = 6.869 03(11) to 6. 7630(5) Å, and V = 802.23(3) Å3 to 778.17(15) Å3, respectively. In the Ba5SrR2Co4O15 series (R = La to Gd), the unit-cell parameters decrease from a = 11.735 44(14) Å to 11.619 79(12) Å, c = 6.942 89 (14) Å to 6.836 52(8) Å, and V = 828.08(3) Å3 to 799.40(2) Å3. In the general structure of (Ba6−xSrx)R2Co4O15, there are four Co ions per formula unit occupying one CoO6 octahedral and three CoO4 tetrahedral units. Through corner-sharing of these polyhedra, a larger Co4O15 unit is formed. Sr2+ ions adopt both octahedral and 8-fold coordination environment. R3+ ions adopt 8-fold coordination (mixed site with Sr), while the larger Ba2+ ions assume both 10- and 11-fold coordination environments. The samples were found to be insulators. X-ray diffraction patterns of these samples have been determined and submitted to the Powder Diffraction File (PDF).

The phase diagram of the La–Ca–Co–O system at 885 °C in air has been determined. The system consists of two materials that have interesting thermoelectric properties, namely, the misfit layered thermoelectric oxide solid solution, (Ca,La)3Co4O9, and Ca3Co2O6 which consists of 1D chains of alternating CoO6 trigonal prism and CoO6 octahedra. The reported La2CaO4 and the Ca-doped (La,Ca)2CoO4−z phases were not found at 885 °C. As a result of the absence of these phases, the phase diagram is significantly different from that reported at 1100 °C. Small solid solution regions of (La1−xCax)2O3−z (0 ≤ x ≤ 0.08), (Ca1−xLax)3Co4O9 (0 ≤ x ≤ 0.07), and (La1−xCax)CoO3−z (0 ≤ x ≤ 0.2) were established.

Phase diagrams and X-ray powder diffraction patterns provide critical information for thermoelectric (TE) research. We have conducted a survey of phase diagrams and powder diffraction patterns of TE systems in the ASM (American Society for Metals) Metal/Alloy database and ICDD (International Centre for Diffraction Data) PDF (Powder Diffraction File), respectively, for their availability and crystal systems. In this report, we focus on TE materials that have the half-HeuslerXYZstructure, and related compounds, based on a set of materials selection rules. We found that among 306 potentialXYZcompounds that we have surveyed, 234 have powder diffraction patterns in the PDF, but only 28 have phase diagram information, and 67 do not have any crystallographic information. Among the 234 phases with powder patterns, 84 were reported to have cubicF43mhalf-Heusler type structure, and the remainder have hexagonal, orthorhombic or other structure types. SomeXYZcompounds have both cubic and hexagonal phases. This information will provide the basis for future activities for the improvement of the databases. These activities include filling the missing gaps in both phase equilibria database and the PDF, as well as adding TE and pertinent physical properties to the PDF.

This paper provides an evaluation of the effectiveness of using the high throughput combinatorial approach for preparing phase diagrams of thin film and bulk materials. Our evaluation is based primarily on examples of combinatorial phase diagrams that have been reported in the literature as well as based on our own laboratory experiments. Various factors that affect the construction of these phase diagrams are examined. Instrumentation and analytical approaches needed to improve data acquisition and data analysis are summarized.

The pillared layer motif is a commonly used route to porous coordination polymers or metal organic frameworks (MOFs). Materials based on the pillared cyano-bridged architecture, [Ni’(L)Ni(CN)4]n (L = pillar organic ligands), also known as PICNICs, have been shown to be especially diverse where pore size and pore functionality can be varied by the choice of pillar organic ligand. In addition, a number of PICNICs form soft porous structures that show reversible structure transitions during the adsorption and desorption of guests. The structural flexibility in these materials can be affected by relatively minor differences in ligand design, and the physical driving force for variations in host-guest behavior in these materials is still not known. One key to understanding this diversity is a detailed investigation of the crystal structures of both rigid and flexible PICNIC derivatives. This article gives a brief review of flexible MOFs. It also reports the crystal structures of five PICNICS from our laboratories including three 3-D porous frameworks (Ni-Bpene, NI-BpyMe, Ni-BpyNH2), one 2-D layer (Ni-Bpy), and one 1-D chain (Ni-Naph) compound. The sorption data of BpyMe for CO2, CH4 and N2 is described. The important role of NH3 (from the solvent of crystallization) as blocking ligands which prevent the polymerization of the 1-D chains and 2-D layers to become 3D porous frameworks in the Ni-Bpy and Ni-Naph compounds is also addressed.

Preface.- Introduction to Solar Cells.- c-Si Based Solar Cells.- Amorphous Si Thin Film Solar Cells.- Single Crystalline Si Thin Film Solar Cells.- II-VI (CdTe) Based Thin Film Solar Cells.- II-II-VI (CuInSe2) Based Thin Film Solar Cells.- III-V (GaAs) Based Thin Film Solar Cells.- Earth Abundant Cu2ZnSn(S,Se)4 (CZTSS) Solar Cells.- Dye Sensitized Solid-State Heterojunction Solar Cells.- Polymer-Inorganic Based Solar Cells.- Organic Solar Cells.- Photoelectrochemical Solar Cells.- Other Semiconductor Materials.- Index.

M2(dhtp)·nH2O (M = Mn, Co, Ni, Zn; dhtp = 2,5-dihydroxyterephthalate), known as MOF74, is a family of excellent sorbent materials for CO2 that contains coordinatively unsaturated metal sites and a honeycomb-like structure featuring a broad one-dimensional channel. This paper describes the structural feature and provides reference X-ray powder diffraction patterns of these four isostructural compounds. The structures were determined using synchrotron diffraction data obtained at beam line 11-BM at the Advanced Photon Source (APS) in the Argonne National Laboratory. The samples were confirmed to be hexagonal R 3 (No. 148). From M = Mn, Co, Ni, to Zn, the lattice parameter a of MOF74 ranges from 26.131 73(4) Å to 26.5738(2) Å, c from 6.651 97(5) to 6.808 83(8) Å, and V ranges from 3948.08 Å3 to 4163.99 Å3, respectively. The four reference X-ray powder diffraction patterns have been submitted for inclusion in the Powder Diffraction File (PDF).

The crystal structure of type I clathrate Ba8Ni4Ge42 has been determined using neutron powder diffraction, transmission electron microscopy (TEM, for possible superlattice), and extended X-ray absorption fine structure (EXAFS) measurements. Ba8Ni4Ge42 is cubic with the space group Pmn and unit-cell parameter a = 10.6769(2) Å (Dx = 5.988 g cm−3). The structure combines two different types of polyhedra: the dodecahedron (Ge20, 20-atom cage with 12 pentagonal faces) and the tetrakaidecahedron (Ge24, 24-atom cage with 12 pentagonal and 2 hexagonal faces). Each unit cell contains two Ge20 dodecahedra and six Ge24 tetrakaidecahedra. The Ge20 dodecahedra are linked via the interstitial 6c positions. The framework structure is formed by a tetrahedrally bounded network of Ge atoms, whereas Ba atoms reside inside the Ge20 and Ge24 cavities at the 2a and 6d crystallographic positions, respectively. Ni atoms exclusively occupy the 6c positions located on the hexagonal faces of the larger tetrakaidecahedra; no Ni atoms are found in the smaller dodecahedra that consist of pentagonal faces. A local structure study using EXAFS supports the coexistence of Ge and Ni on the 6c site. Electron diffraction in TEM reveals no detectable Ge/Ni ordering.

The selective adsorption of CO{sub 2} from mixtures with N{sub 2}, CH{sub 4}, and N{sub 2}O in a dynamic porous coordination polymer (see monomer structure) was evaluated by ATR-FTIR spectroscopy, GC, and SANS. All three techniques indicate highly selective adsorption of CO{sub 2} from CO{sub 2}/CH{sub 4} and CO{sub 2}/N{sub 2} mixtures at 30 C, with no selectivity observed for the CO{sub 2}/N{sub 2}O system.