Yb Substitution and Ultralow Thermal Conductivity of the Ca3-xYbxAlSb3 (0 ≤ x ≤ 0.81(1)) System.

A series of Yb-substituted Zintl phases in the Ca3-xYbxAlSb3 (0 ≤ x ≤ 0.81(1)) system has been synthesized by initial arc melting and post-heat treatment, and their isotypic crystal structures were characterized by both powder and single crystal X-ray diffraction analysis. All four title compounds adopted the Ca3AlAs3-type structure (space group Pnma, Pearson code oP28, Z = 4). The overall structure can be described as a combination of the 1-dimensional (1D) infinite chain of ∞1[Al(Sb2Sb2/2)] formed by two vertices sharing [AlSb4] tetrahedral moieties and three Ca2+/Yb2+ mixed sites located in between these 1D chains. The charge balance and the resultant independency of the 1D chains in the title system were explained by the Zintl-Klemm formalism [Ca2+/Yb2+]3[(4b-Al1-)(1b-Sb2-)2(2b-Sb1-)2/2]. A series of DFT calculations proved that (1) the band overlap between the d-orbital states from two types of cations and the p-orbital states from Sb at the high symmetry Γ point implied a heavily doped degenerate semiconducting behavior of the quaternary Ca2YbAlSb3 model and (2) the site preference of Yb for the M1 site was due to the electronic-factor criterion based on the Q values of each atomic site. The electron localization function calculations also proved that the two different shapes of lone pairs of the Sb atoms─the "umbrella-shape" and the "C-shape"─are determined by local geometry and the coordination environment on the anionic frameworks. Thermoelectric measurements of the quaternary title compound Ca2.19(1)Yb0.81AlSb3 showed an approximately two times larger ZT value than that of ternary Ca3AlSb3 at 623 K due to increased electrical conductivity and ultralow thermal conductivity originated from Yb substitution for Ca.

Experimental and Theoretical Study on the Nonmagnetic Li/Mg Cosubstitution in the Gd5-x(Li/Mg)xGe4 (x = 1.04, 1.17, 1.53) System.

Three Li- and Mg-cosubstituted compounds in the Gd5-x(Li/Mg)xGe4 (x = 1.04(2), 1.17(2), 1.53(2)) system have been successfully prepared by conventional high-temperature reactions. According to powder and single-crystal X-ray diffraction analyses, all three compounds adopt a Gd5Si4-type phase with the orthorhombic Pnma space group (Pearson code oP16, Z = 4) and six crystallographically independent atomic sites. The crystal structure can be described as a combination of two-dimensional Mo2FeB2-type ∞2[Gd2(Li/Mg)Ge2] layers and [Ge2] dimers. Interestingly, as 64% of Li and 26% of Gd at the RE3 and RE2 sites, respectively, were exclusively substituted by Mg in Gd3.47(1)Li0.36(2)Mg1.17(3)Ge4, the lattice parameter b was selectively shortened as a result of the RE3-Ge1 bond shrinkage in comparison to that in Gd4LiGe4, while lattice parameters a and c remained nearly intact. A series of theoretical calculations using the tight-binding linear muffin-tin orbital (TB-LMTO) method indicated that the reduction of the particular RE3-Ge1 bond distance in the title compounds could also be explained by an optimization of bonding based on the corresponding RE3-Ge1 crystal orbital Hamilton population (COHP) curve. Moreover, the specific site preference of Mg for the RE3 site was supported by both size-factor as well as electronic-factor criteria on the basis of the smallest atomic size and the highest electronegativity of Mg among the three cations. Therefore, the overall electronic structure was further interrogated by a density of states (DOS) analysis. The influence of nonmagnetic Li/Mg cosubstitution for the magnetic Gd atoms in the title Gd5-x(Li/Mg)xGe4 system on the magnetic characteristics was also thoroughly studied by isofield magnetization at 100 Oe and 10 kOe and isothermal magnetization measurements at 4 K using two of the title compounds: Gd3.83(1)Li0.48Mg0.69(3)Ge4 and Gd3.47(1)Li0.36(2)Mg1.17(3)Ge4.

p-Type Double Doping and the Diamond-like Morphology Shift of the Zintl Phase Thermoelectric Materials: The Ca11-xAxSb10-yGez (A = Na, Li; 0.06(3) ≤ x ≤ 0.17(5), 0.19(1) ≤ y ≤ 0.55(1), 0.13(1) ≤ z ≤ 0.22(1)) System.

Five ternary and quaternary Zintl phases in the solid-solution Ca11-xAxSb10-yGez (A = Na, Li; 0.06(3) ≤ x ≤ 0.17(5), 0.19(1) ≤ y ≤ 0.55(1), 0.13(1) ≤ z ≤ 0.22(1)) system have been successfully synthesized by both of the arc-melting and the molten Pb metal-flux reactions. The crystal structure of these title compounds was characterized by powder and single-crystal X-ray diffractions analyses, and all title compounds crystallized in the Ho11Ge10-type phase in the tetragonal space group I4/mmm (Z = 4, Pearson code tI84). The complex crystal structure can be described as an assembly of 1) three kinds of cationic polyhedra centered by three different Sb and 2) the cage-shaped anionic frameworks built through the connection of two types of Sb. The newly substituted p-type double dopants of the cationic (Na and Li) and anionic (Ge) elements displayed particular site preferences, which were successfully explained by either the size-factor criterion based on the atomic size or the electronic-factor criterion based on the electronegativity of an element. Quite interestingly, as the reaction conditions were changed, the morphology shift of single crystals in Ca10.94(3)Na0.06Sb9.58(1)Ge0.21 occurred from a cubic-shaped to a hummocky-type, to a hopper-type, and eventually to an octahedral-shaped crystal, just like the Yakutian kimberlite diamonds. Moreover, we firmly believe that the inclusion of the p-type Ge dopant for Sb was crucial to trigger this type of morphology shift and complete the octahedral-shaped morphology in the overall crystal-growth mechanism. The theoretical calculations using a DFT method rationalized the observed site preference of Na and the electronic effect of the p-type Ge dopants. The Seebeck coefficient measurements for Ca10.88(4)Li0.12Sb9.45(1)Ge0.21 indicated that some portions of electron charge carriers were effectively eliminated by the p-type double dopants using Li and Ge.

Two Steps to Improve the Thermoelectric Performance of the Ca5-xYbxAl2-yInySb6 System.

A series of quaternary and quinary Zintl phase thermoelectric (TE) compounds, Ca5-xYbxAl2-yInySb6 (3.07(1) ≤ x ≤ 4.88(2); 0.16(2) ≤ y ≤ 2.00), containing Al/In mixed sites as well as Ca/Yb mixed sites has been successfully synthesized by a direct arc-melting method, and the X-ray diffraction analyses indicated that the products initially adopted an orthorhombic Ba5Al2Bi6-type structure (space group Pbam, Z = 2). However, after a postannealing process at 973 K for 1 month, the particular Yb rich compounds underwent a transformation of the original structure type to a Ca5Ga2Sb6-type phase regardless of the In substitution for Al. The noticeable site preference of cationic Ca and Yb in the three available cationic sites could be understood on the basis of a size match between the central cation and the volume of the anionic polyhedra. The observed phase transition was nicely explained by DFT calculations, proving that the Ca5Ga2Sb6-type phase was energetically more favorable than the Ba5Al2Sb6-type phase for the particular Yb-rich compound. Moreover, this energy difference between the two title phases was originally the result of both the site energy in the Ca site and the bond energies in the [(Al/In)2Sb8] anionic building blocks. A series of thermoelectric property data indicated that a two-step process involving a partial/full In substitution for Al and a phase transition from the Ba5Al2Sb6-type to the Ca5Ga2Sb6-type phase successfully enhanced the electrical conductivities and the Seebeck coefficients of the title compounds. This kind of combined effect eventually resulted in a ZT improvement for the quinary compound Ca1.14(2)Yb3.86Al1.68(1)In0.32Sb6 by approximately 4 times in comparison to its quaternary predecessor Ca1.55(1)Yb3.45Al2Sb6.

Anionic Doping and Cationic Site Preference in CaYb4Al2Sb6- xGe x ( x = 0.2, 0.5, 0.7): Origin of the Enhanced Seebeck Coefficient and the Structural Transformation.

Three Zintl phase compounds belonging to the CaYb4Al2Sb6- xGe x ( x = 0.2, 0.5, 0.7; nominal compositions) system with various Ge-doping contents were successfully synthesized by arc-melting and were initially crystallized in the Ba5Al2Bi6-type phase (space group Pbam, Pearson codes oP26). However, after post-heat treatment at an elevated temperature, the originally obtained crystal structure was transformed into the homeotypic Ca5Ga2Sb6-type structure according to powder and single-crystal X-ray diffraction analyses. Two types of crystal structures share some isotypic structural moieties, such as the one-dimensional anionic chains formed by ∞1[Al2Sb8] and the void-filling Ca2+/Yb2+ mixed cations, but the slightly different spatial arrangements in each unit cell make these two structural types distinguishable. This series of title compounds is originally investigated to examine whether anionic p-type doping using Ge can successfully enhance thermoelectric (TE) properties of the Yb-rich CaYb4Al2Sb6- xGe x series even after the phase transition from the Ba5Al2Bi6-type to the Ca5Ga2Sb6-type phase. More interestingly, we also reveal that the given structural transformation is triggered by the particularly different site-preference of Ca2+ and Yb2+ among three available cationic sites in each structure type, which is significantly affected by thermodynamic conditions of this system. Band structure and density of states analyses calculated by density functional theory using the tight-binding linear muffin-tin orbital method also prove that the Ge-doping actually increases band degeneracies and the number of resonant peaks near the Fermi level resulting in the improvement of Seebeck coefficients. Electron localization function analyses for the (0 1 0) sliced-plane and the 3D isosurface nicely illustrates the distortion of the paired-electron densities due to the introduction of Ge. The systematic TE property measurements imply that the attempted anionic p-type doping is indeed effective to improve the TE characteristics of the title CaYb4Al2Sb6- yGe y system.

Layered Bismuth Oxyfluoride Nitrates Revealing Large Second-Harmonic Generation and Photocatalytic Properties.

Two novel bismuth oxyfluoride nitrates, Bi2OF3(NO3) and Bi6O6F5(NO3), have been synthesized via hydrothermal reactions. Whereas Bi2OF3(NO3) crystallizes in the centrosymmetric (CS) hexagonal space group, P63/ m, Bi6O6F5(NO3) crystallizes in the polar noncentrosymmetric (NCS) trigonal space group, R3. The backbones of the title compounds reveal double layered structures composed of asymmetric BiF3(O/F)3 or BiO3F2 polyhedra and NO3 trigonal planar groups. The diffuse reflectance spectra indicate that Bi2OF3(NO3) and Bi6O6F5(NO3) contain wide band gaps of 3.5 and 4.0 eV, respectively. Powder second-harmonic generation (SHG) measurements suggest that NCS Bi6O6F5(NO3) is Type-I phase-matchable and has a large SHG response of ca. 3 times that of KH2PO4 (KDP). Electron localization function (ELF) analysis indicates that the large SHG efficiency of Bi6O6F5(NO3) is attributed to the synergistic effect of the alignment of NO3- trigonal planar groups and strong interactions between highly polarizable lone pair electrons on Bi3+ and π-delocalized electrons in NO3- groups. Bi2OF3(NO3) also exhibits a very good photocatalytic degradation efficiency of Rhodamine B (RhB) under the UV light irradiation.

Rb3 VO(O2 )2 CO3 : A Four-in-One Carbonatoperoxovanadate Exhibiting an Extremely Strong Second-Harmonic Generation Response.

A nonlinear optical (NLO) carbonatoperoxovanadate, Rb3 VO(O2 )2 CO3 , was synthesized through a simple solution-evaporation method in phase-pure form. Single-crystal X-ray diffraction revealed that the structure of Rb3 VO(O2 )2 CO3 consists of important noncentrosymmetric (NCS) chromophores, that is, π-delocalized (CO3 )2- groups, a second-order Jahn-Teller (SOJT) distortive V5+ cation, and π-localized distorted O22- groups, as well as charge-balancing polarizable Rb+ ions. The powder second-harmonic generation (SHG) measurements indicated that Rb3 VO(O2 )2 CO3 is phase-matchable (Type I) and exhibits a remarkably strong SHG response circa 21.0 times that of potassium dihydrogen phosphate (KDP), which is the largest efficiency observed among carbonate NLO materials. First-principles calculation analysis suggests that the extremely large SHG response of Rb3 VO(O2 )2 CO3 is attributed to the synergistic effect of the cooperation of all the constituting NCS chromophores.

Structure and Chemical Bonding of the Li-Doped Polar Intermetallic RE2In1-xLixGe2 (RE = La, Nd, Sm, Gd; x = 0.13, 0.28, 0.43, 0.53) System.

Four polar intermetallic compounds belonging to the RE2In1-xLixGe2 (RE = La, Nd, Sm, Gd; x = 0.13(1), 0.28(1), 0.43(1), 0.53(1)) system have been synthesized by the traditional solid-state reaction method, and their crystal structures have been characterized by single-crystal X-ray diffraction (SXRD) analyses. The isotypic crystal structures of four title compounds adopt the Mo2FeB2-type structure having the tetragonal space group P4/mbm (Z = 2, Pearson code tP40) with three crystallographically independent atomic sites and can be simply described as a pile of the identical 2-dimensioanl (2D) RE2In1-xLixGe2 slabs stacked along the c-axis direction. The substituting Li atom shows a particular site preference for replacing In at the Wyckoff 2a site rather than Ge at the Wyckoff 4g in this crystal structure. As the size of a used rare-earth metal decreases from La3+ to Gd3+ throughout the title system, the Ge-Ge and Ge-In/Li bond distances, both of which consist of the 2D anionic Ge2(In/Li) layer, gradually decrease resulting in the reduction of a unit cell volume. A series of theoretical investigations has been performed using a hypothetical structure model Gd2In0.5Li0.5Ge2 by tight-binding linear muffin-tin orbital (TB-LMTO) method. The resultant densities of states (DOS) value at the Fermi level (EF) suggests a metallic conductivity for this particular composition, and this calculation result is in a good agreement with the formal charge distribution assigning two extra valence electrons for a metal-metal bond in the conduction band. The thorough analyses of six crystal orbital Hamilton population (COHP) curves representing various interatomic interactions and an electron localization function (ELF) diagram indicating the locations of paired-electron densities are also provided in this article.

From a Metastable Layer to a Stable Ring: A Kinetic Study for Transformation Reactions of Li2 Mo3 TeO12 to Polyoxometalates.

A metastable tellurite, Li2 Mo3 TeO12 , revealing a corrugated layered structure in an extremely strained coordination environment was hydrothermally synthesized in high yield. Li2 Mo3 TeO12 undergoes Li+ -exchange-driven facile structural transformation reactions to polyoxometalates. The kinetic data for the transformation reactions at various conditions were successfully obtained by simple lab-source powder X-ray diffraction. The investigation suggests that the solid-state transformation reactions may occur through a series of steps; substitution, decomposition, recombination, and precipitation. This new finding could be utilized in discovering functional metastable materials as well as understanding their phase transition mechanisms.

Cs3VO(O2)2CO3: an exceptionally thermostable carbonatoperoxovanadate with an extremely large second-harmonic generation response.

A novel nonlinear optical (NLO) carbonatoperoxovanadate, Cs3VO(O2)2CO3, with an exceptionally high thermostability was successfully synthesized by introducing highly polarizable Cs+ cations and inorganic polydentate carbonate anions into asymmetric peroxovanadates. The structure of Cs3VO(O2)2CO3 is composed of distorted [VO(O2)2CO3]3- units and charge balancing Cs+ cations. The title compound exhibits the largest NLO intensity ever found in the current carbonate NLO materials, i.e., 23.0 times that of KH2PO4 (KDP). The remarkably strong second-harmonic generation (SHG) response originates from the synergistic effect of the exceedingly polarizable Cs+ cations, distortive polyhedra of the V5+ cation, delocalized π orbitals in CO3 groups, and distorted localized π orbitals in O2 groups. First-principles calculations indicated that introducing the polarizable cations into peroxovanadates not only induces the enhancement of the SHG response but also improves the thermal stability of the framework.

Single and double-doping effects on the thermoelectric properties of two Zintl compounds: Eu11Bi8.07(2)Sn1.93 and Eu10.74(2)K0.26Bi9.14(2)Sn0.86.

Two Zintl phase thermoelectric compounds of Eu11-xKxBi10-ySny (x = 0, 0.26(1); y = 0.86(2), 1.93(2)) have been synthesized by a high-temperature solid-state reaction and arc-melting methods. The two isotypic crystal structures are characterized by both single-crystal and powder X-ray diffractions, and adopt a tetragonal Ho11Ge10-type structure (space group I4/mmm, Z = 2, Pearson code tI84) containing nine crystallographically independent asymmetric atomic sites in a unit cell. The chemical compositions are confirmed by EDS analysis. The complex crystal structure of the two title compounds can be described as an assembly of three different types of co-facial polyhedra formed by cations and 3-dimensional anionic frameworks surrounding these polyhedra. A quaternary title compound, Eu10.74(2)K0.26Bi9.14(2)Sn10.86, which simultaneously contains both cationic and anionic p-dopants in a single compound, was successfully crystallized for the first time in the A11M10 (A = alkaline-earth metals, rare-earth metals; M = triels, tetrels, pnictogens) series. In particular, two different types of p-dopants K and Sn show particular site-preferences, respectively, where K and Sn prefer to occupy the cationic Wyckoff 4e site and the anionic Wyckoff 8h site. These noticeable site preferences can be elucidated by either a size-factor criterion for the K-doping case or by an electronic-factor criterion for the Sn-doping case. The tight-binding linear muffin-tin orbital calculations show that as the double p-doping is applied to the Eu11-xKxBi10-ySny system, some extra holes are generated on the electronic structures according to the density of states curves. However, a series of thermoelectric property measurements prove that this extra hole-carrier doping is hardly effective enough to completely suppress a bipolar conduction of holes and electrons due to the rigid metallic band structure of the title system.

Effect of MultiSubstitution on the Thermoelectric Performance of the Ca11-xYbxSb10-yGez (0 ≤ x ≤ 9; 0 ≤ y ≤ 3; 0 ≤ z ≤ 3) System: Experimental and Theoretical Studies.

The Zintl phase solid-solution Ca11-xYbxSb10-yGez (0 ≤ x ≤ 9; 0 ≤ y ≤ 3; 0 ≤ z ≤ 3) system with the cationic/anionic multisubstitution has been synthesized by molten Sn metal flux and arc-melting methods. The crystal structure of the nine title compounds were characterized by both powder and single-crystal X-ray diffractions and adopted the Ho11Ge10-type structure with the tetragonal space group I4/mmm (Z = 4, Pearson Code tI84). The overall isotypic structure of the nine title compounds can be illustrated as an assembly of three different types of cationic polyhedra sharing faces with their neighboring polyhedra and the three-dimensional cage-shaped anionic frameworks consisting of the dumbbell-shaped Sb2 units and the square-shaped Sb4 or (Sb/Ge)4 units. During the multisubstitution trials, interestingly, we observed a metal-to-semiconductor transition as the Ca and Ge contents increased in the title system from Yb11Sb10 to Ca9Yb2Sb7Ge3 (nominal compositions) on the basis of a series of thermoelectric property measurements. This phenomenon can be elucidated by the suppression of a bipolar conduction of holes and electrons via an extra hole-carrier doping. The tight-binding linear muffin-tin orbital calculations using four hypothetical structural models nicely proved that the size of a pseudogap and the magnitude of the density of states at the Fermi level are significantly influenced by substituting elements as well as their atomic sites in a unit cell. The observed particular cationic/anionic site preferences, the historically known abnormalities of atomic displacement parameters, and the occupation deficiencies of particular atomic sites are further rationalized by the QVAL value criterion on the basis of the theoretical calculations. The results of SEM, EDS, and TGA analyses are also provided.

Pb2 BO3 Cl: A Tailor-Made Polar Lead Borate Chloride with Very Strong Second Harmonic Generation.

A meticulously designed, polar, non-centrosymmetric lead borate chloride, Pb2 BO3 Cl, was synthesized using KBe2 BO3 F2 (KBBF) as a model. Single-crystal X-ray diffraction revealed that the structure of Pb2 BO3 Cl consists of cationic [Pb2 (BO3 )](+) honeycomb layers and Cl(-) anions. Powder second harmonic generation (SHG) measurements on graded polycrystalline Pb2 BO3 Cl indicated that the title compound is phase-matchable (type I) and exhibits a remarkably strong SHG response, which is approximately nine times stronger than that of potassium dihydrogen phosphate, and the largest efficiency observed in materials with structures similar to KBBF. Further characterization suggested that the compound melts congruently at high temperature and has a wide transparency window from the near-UV to the mid-IR region.

Cationic Site-Preference in the Yb14-xCaxAlSb11 (4.81 ≤ x ≤ 10.57) Series: Theoretical and Experimental Studies.

Four quaternary Zintl phases with mixed-cations in the Yb14-xCaxAlSb11 (4.81 ≤ x ≤ 10.57) series have been synthesized by using the arc-melting and the Sn metal-flux reaction methods, and the isotypic crystal structures of the title compounds have been characterized by both powder and single-crystal X-ray diffraction (PXRD and SXRD) analyses. The overall crystal structure adopting the Ca14AlSb11-type can be described as a pack of four different types of the spiral-shaped one-dimensional octahedra chains with various turning radii, each of which is formed by the distorted ((Yb/Ca)Sb6) octahedra. Four symmetrically-independent cationic sites contain mixed occupations of Yb2+ and Ca2+ with different mixing ratios and display a particular site preference by two cationic elements. Two hypothetical structural models of Yb4Ca10AlSb11 with different cationic arrangements were designed and exploited to study the details of site and bond energies. QVAL values provided the rationale for the observed site preference based on the electronegativity of each atom. Density of states (DOS) curves indicated a semiconducting property of the title compounds, and crystal orbital Hamilton population (COHP) plots explained individual chemical bonding between components. Thermal conductivity measurement was performed for Yb8.42(4)Ca5.58AlSb11, and the result was compared to compounds without mixed cations.

Crystal structure, chemical bonding and magnetism studies for three quinary polar intermetallic compounds in the (Eu(1-x)Ca(x))9In8(Ge(1-y)Sn(y))8 (x = 0.66, y = 0.03) and the (Eu(1-x)Ca(x))3In(Ge(3-y)Sn(1+y)) (x = 0.66, 0.68; y = 0.13, 0.27) phases.

Three quinary polar intermetallic compounds in the (Eu(1-x)Ca(x))9In8(Ge(1-y)Sn(y))8 (x = 0.66, y = 0.03) and the (Eu(1-x)Ca(x))3In(Ge(3-y)Sn(1+y)) (x = 0.66, 0.68; y = 0.13, 0.27) phases have been synthesized using the molten In-metal flux method, and the crystal structures are characterized by powder and single-crystal X-ray diffractions. Two orthorhombic structural types can be viewed as an assembly of polyanionic frameworks consisting of the In(Ge/Sn)4 tetrahedral chains, the bridging Ge2 dimers, either the annulene-like "12-membered rings" for the (Eu(1-x)Ca(x))9In8(Ge(1-y)Sn(y))8 series or the cis-trans Ge/Sn-chains for the (Eu(1-x)Ca(x))3In(Ge(3-y)Sn(1+y)) series, and several Eu/Ca-mixed cations. The most noticeable difference between two structural types is the amount and the location of the Sn-substitution for Ge: only a partial substitution (11%) occurs at the In(Ge/Sn)4 tetrahedron in the (Eu(1-x)Ca(x))9In8(Ge(1-y)Sn(y))8 series, whereas both a complete and a partial substitution (up to 27%) are observed, respectively, at the cis-trans Ge/Sn-chain and at the In(Ge/Sn)4 tetrahedron in the (Eu(1-x)Ca(x))3In(Ge(3-y)Sn(1+y)) series. A series of tight-binding linear muffin-tin orbital calculations is conducted to understand overall electronic structures and chemical bonding among components. Magnetic susceptibility measurement indicates a ferromagnetic ordering of Eu atoms below 5 K for Eu1.02(1)Ca1.98InGe2.87(1)Sn1.13.

Single-crystal growth and size control of three novel polar intermetallics: Eu2.94(2)Ca6.06In8Ge8, Eu3.13(2)Ca5.87In8Ge8, and Sr3.23(3)Ca5.77In8Ge8 with crystal structure, chemical bonding, and magnetism studies.

Three new quaternary polar intermetallic compounds of Eu2.94(2)Ca6.06In8Ge8, Eu3.13(2)Ca5.87In8Ge8, and Sr3.23(3)Ca5.77In8Ge8 have been synthesized by a metal-flux method using molten indium metal as a reactive flux, and the novel isotypic crystal structures have been characterized by both powder and single-crystal X-ray diffractions. All compounds crystallize in the orthorhombic space group Pmmn (Z = 2, Pearson symbol oP50) with 14 crystallographically unique atomic positions in the asymmetric unit. The lattice parameters are refined as follows: a = 36.928(2) Å, b = 4.511(1) Å, and c = 7.506(1) Å for Eu2.94(2)Ca6.06In8Ge8; a = 37.171(19) Å, b = 4.531(2) Å, and c = 7.560(4) Å for Eu3.13(2)Ca5.87In8Ge8; and a = 37.350(2) Å, b = 4.550(3) Å, and c = 7.593(4) Å for Sr3.23(3)Ca5.77In8Ge8. In particular, single crystals of two Eu-containing compounds are obtained as bundles of bar/needle-shaped crystals, and the thicknesses of those crystals can be controlled in the range between ca. 300 µm and ca. <10 µm by adjusting several reaction conditions, including the reaction cooling rate and the centrifugation temperature. The overall crystal structure is illustrated as an assembly of (1) the three-dimensional anionic framework, which is formed by the chains of edge-sharing InGe4 tetrahedra and the annulene-like "12-membered anionic rings" connected via Ge2 dimers, and (2) the cationic mixed sites embedded in the space between the anionic frameworks. Theoretical investigations based on tight-binding linear muffin-tin orbital (TB-LMTO) calculations provide a comprehesive understanding of the overall electronic structure and chemical bonding observed among anionic components and between anions and cations. Electron localization function (ELF) and electron density map present chemical bond strengths and polarization within the anionic framework. Magnetic susceptibility measurement proves an antiferromagnetic (AFM) ordering of Eu atoms below 4 K with a reduced effective magnetic moment of 7.12 µB for the Eu atom.

Lead sulfide nanocrystal quantum dot solar cells with trenched ZnO fabricated via nanoimprinting.

The improvement of power conversion efficiency, especially current density (Jsc), for nanocrystal quantum dot based heterojunction solar cells was realized by employing a trenched ZnO film fabricated using nanoimprint techniques. For an optimization of ZnO patterns, various patterned ZnO films were investigated using electrical and optical analysis methods by varying the line width, interpattern distance, pattern height, and residual layer. Analyzing the features of patterned ZnO films allowed us to simultaneously optimize both the pronounced electrical effects as well as optical properties. Consequently, we achieved an enhancement in Jsc from 7.82 to 12.5 mA cm(-2) by adopting the patterned ZnO with optimized trenched shape.

Synthesis, crystal structures and chemical bonding of RE(5-x)Li(x)Ge4 (RE = Nd, Sm and Gd; x ≃ 1) with the orthorhombic Gd5Si4 type.

The syntheses and single-crystal and electronic structures of three new ternary lithium rare earth germanides, RE(5-x)Li(x)Ge(4) (RE = Nd, Sm and Gd; x ≃ 1), namely tetrasamarium lithium tetragermanide (Sm(3.97)Li(1.03)Ge(4)), tetraneodymium lithium tetragermanide (Nd(3.97)Li(1.03)Ge(4)) and tetragadolinium lithium tetragermanide (Gd(3.96)Li(1.03)Ge(4)), are reported. All three compounds crystallize in the orthorhombic space group Pnma and adopt the Gd(5)Si(4) structure type (Pearson code oP36). There are six atoms in the asymmetric unit: Li1 in Wyckoff site 4c, RE1 in 8d, RE2 in 8d, Ge1 in 8d, Ge2 in 4c and Ge3 in 4c. One of the RE sites, i.e. RE2, is statistically occupied by RE and Li atoms, accounting for the small deviation from ideal RE(4)LiGe(4) stoichiometry.

Experimental and theoretical investigations of the novel ternary compound Ca4InGe4.

A new polar intermetallic compound with a novel structure type has been synthesized and characterized by both powder and single-crystal X-ray diffraction. Ca(4)InGe(4) crystallizes in the monoclinic crystal system (space group C2/c, Z = 4, Pearson symbol mS36) with five crystallographically unique atomic positions in the asymmetric unit. The corresponding lattice parameters at 200(2) K are a = 18.452(8) Å, b = 5.819(2) Å, c = 8.339(3) Å, and ß = 99.330(6)°. The overall crystal structure can be described as a linear intergrowth of two imaginary fragments--Ca(2)InGe(2) with the Gd(2)AlGe(2) type- and CaGe with the FeB type-structures. Another way to rationalize the bonding is to focus on the polyanionic framework, which in this case is made up of unique nets of "seesaw"-shaped [InGe(4)] units. They are interconnected via Ge-Ge dimers into an open three-dimensional framework with Ca(2+) cations occupying the voids within it. Tight-binding linear muffin-tin orbital (LMTO) calculations provide a rationale for the unique local coordination geometry around In and the two distinct types of Ge-Ge bond distances.

Synthesis, crystal chemistry, and magnetic properties of RE7Li8Ge10 and RE11Li12Ge16 (RE = La-Nd, Sm): new members of the [REGe2](n)[RELi2Ge](m) homologous series.

Eight new rare-earth metal-lithium-germanides belonging to the [REGe(2)](n)[RELi(2)Ge](m) homologous series have been synthesized and structurally characterized by single-crystal X-ray diffraction. The structures of the title compounds can be rationalized as linear intergrowths of imaginary RELi(2)Ge (MgAl(2)Cu structure type) and REGe(2) (AlB(2) structure type) slabs. The compounds with general formula RE(7)Li(8)Ge(10) (RE = La-Nd, Sm), i.e., [REGe(2)](3)[RELi(2)Ge](4), crystallize in the orthorhombic space group Cmmm (No. 65) with a new structure type. Similarly, the compounds with general formula RE(11)Li(12)Ge(16) (RE = Ce-Nd), i.e., [REGe(2)](5)[RELi(2)Ge](6), crystallize in the orthorhombic space group Immm (No. 71) also with its own structure type. Temperature-dependent DC magnetization measurements indicate Curie-Weiss paramagnetism in the high-temperature regime and hint at complex magnetic ordering at low temperatures. The measured effective moments are consistent with RE(3+) ground states in all cases. The experimental results have been complemented by tight-binding linear muffin-tin orbital (TB-LMTO) electronic structure calculations.