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A specialized empirical (Spec-zd Emp) system of ionic radii (SIR) for R = Y3+, La3+, Ln3+, and F1− (R rare earth elements (REE)) was derived from the dependence of lanthanide contraction (LC) on the atomic number (Z) of lanthanides (Ln). LC decreased the radius of the cation with increasing Z. The structures of t-RF3 (LaF3-NdF3, "pseudo t-SmF3") of the LaF3 type, 11 β-LnF3 (Ln = Sm-Lu), and β-YF3 of the β-YF3 type were studied. The empirical basis of the shortest (F-F)min and (R-F)min distances was calculated from the structural data for the RF3 complete series. The dependence of (F-F)min on Z reached saturation at Z = 67 (Ho). The base F1− radius r− = 1.2539(16) Å was calculated as the arithmetic mean of five (F-F)min in LnF3 with Ln = Ho-Lu. For the LnF3 series with Ln contributions up to 75 % wt., the dependence of (Ln-F)min on Z reflected the non-uniformity of the 4f orbital filling. SIR was calculated as the difference in the empirical constants of RF3 (ionic radii of (R,Ln)3+ (r+) and F1− (r−)), the change in which was continuous over the series and did not depend on the type of structure: r+ = (ZR-F)min − ½(F-F)min (Z = 57–71). The changes in LC in the LnF3 series were described by a third-degree polynomial. LC reduced r+ by 24% (percentage relative to less) from 1.1671(16) Å (La3+) to 0.9439(17) Å (Lu3+). In the Spec-zd Emp SIR, r+ were constants that did not require corrections for a coordination number (CN). A comparison of r+ in the Spec-zd Emp SIR with other SIRs was performed. [ABSTRACT FROM AUTHOR]

A lanthanide contraction(LC) of 14 lanthanides (Ln) from 58Ce to 71Lu consists of the interaction of Ln nucleus with 4f-electrons. Rare earth elements (REEs—R) include Sc, Y, La, and 14 Ln. They are located in 4–6th periods of the subgroup of group III. The electronic structure divides R into short (d- Sc, Y, La) and long (14 f-elements Ce-Lu) homologous series. The most important chemical consequence of LC is the creation of a new conglomerate of 16 RF3 by mixing fluorides of d- (Y, La) and f-elements. This determines the location of YF3 among LnF3. The location of YF3 depends on the structural (formula volumes—Vform) and thermochemical (temperatures and heats of phase transformations, phase diagrams) properties. The location of YF3 between HoF3 and ErF3 was determined by Vform at a standard pressure (Pst) and temperature (Tst). The location of YF3 according to heats of phase transformations ΔHfus and ΔHtrans is in a dimorphic structural subgroup (SSGr) D (Ln = Er-Lu), but without the exact "pseudo ZY". According to the temperatures of phase transformations (Ttrans) in LnF3 (Ln = Dy-Lu), YF3 is located in the SSGr D between ErF3 and TmF3. The ErF3-YF3 and YF3-TmF3 phase diagrams show it to be between ErF3 and TmF3. The crystals of five β-LnF3 (Ln = Ho-Lu) and β-YF3 were obtained in identical conditions and their crystal structures were studied. Vform (at Pst and Tst) with "pseudo" atomic number ZY = 67.42 was calculated from the unit cell parameters, which were defined with ±5 × 10−4 Å accuracy. It determines the location of YF3 between HoF3 and ErF3. [ABSTRACT FROM AUTHOR]

The structural parameters of the rare-earth diacetate halide trihydrates, RE(OAc)2Hal·3H2O with RE = Ce − (Pm) − Lu and Hal = Cl, Br, have been determined by low temperature, high-resolution SCXRD in order to examine the effect of lanthanide contraction on the coordination geometry in this series of isomorphous compounds consisting of cationic, acetate-bridged, non-linear, one-dimensional coordination polymers of composition [RE(H2O)3(OAc)2]+ and laterally hydrogen bonded halide ions, Hal−. Although the shrinkage of the unit cell volume follows lanthanide contraction very well over the complete range of investigated RE elements, many other parameters (i.e., lattice constants, angles and distances in the RE··· RE alignment, RE-O bond lengths, etc.) exhibit a more complex response on lanthanide contraction often expressed by sigmoid curves that can be ascribed to a continuous transition from CN9 (RE = Ce) to CN8 (RE = Lu) as one acetate group loses the chelate function, an effect accompanied by significant structural changes of the carboxylate group. Therefore, data are best analyzed by use of two subsets represented by the two different structure types of Ce and Lu, the structural features of which change with decreasing/increasing the size of RE3+, up to the borderline between both subsets. [ABSTRACT FROM AUTHOR]

Cycling lithium cobalt oxide (LiCoO2) to a potential higher than 4.35 V (vs Li+/Li) can obtain an enticing capacity, but suffers from inferior structural stability. Herein, an ingenious Li‐deintercalation/doping strategy is developed to synthesize the lanthanide‐doped LiCoO2 (lanthanide (Ln) = praseodymium, neodymium, samarium, europium, gadolinium, erbium, or lutetium) with Ln occupying Li‐sites. Electrochemical measurements show that the cycling stability of Ln‐doped LiCoO2 increases as the lanthanide contracts. By rule, lutetium‐doped LiCoO2 exhibits the best cycling stability, confirmed in both lithium half‐cell and pouch full‐cell. Comprehensive experimental characterizations combining with theoretical calculations reveal that the lattice strain tuned by the lanthanide contraction plays a critical role in the structure stability of LiCoO2. This finding is an important step for building better high‐voltage LiCoO2 batteries, as it is possible to achieve better high‐voltage performance by combining the doping technology and performance improvement rule disclosed in this study. [ABSTRACT FROM AUTHOR]

Four new rare-earth metal–organic frameworks containing thieno[3,2b]thiophene-2,5-dicarboxylate (ttdc2−) with general formulae [M2(DMF)4(ttdc)3] (M3+ = Y3+ for 1, La3+ for 2, Tb3+ for 3) and [M2(H2O)2(ttdc)3] (M3+ = Lu3+ for 4) were synthesized. Their crystal structures were determined by performing a single-crystal X-ray diffraction analysis. Coordination polymers 1–3 are based on the binuclear metal-carboxylate building units with the formulae {M2(DMF)4(OOCR)6}. The six-connected blocks in 1–3 form a three-dimensional network with the primitive cubic (pcu) topology. Coordination framework 4 is based on chains comprised by stretched pseudo-binuclear metal-carboxylate building units. The chains are interconnected in four directions with ttdc2− linkers forming the 3D framework. The luminescent properties were studied for the synthesized frameworks in the solid state. All the coordination frameworks show a broad blue emission band (λex = 380 nm) typical for intra-ligand electron transitions. The sensing properties of 3 dispersions in solutions were investigated in detail and the luminescent response (quenching) was discovered in the presence of cinnamaldehyde and quinoline in diluted solutions at concentrations of as low as 4 × 10−1 vol.% and 4 × 10−2 vol.% (~3 × 10−3 M), respectively. [ABSTRACT FROM AUTHOR]

The structural parameters of the rare-earth diacetate halide trihydrates, RE(OAc)2Hal·3H2O with RE = Ce − (Pm) − Lu and Hal = Cl, Br, have been determined by low temperature, high-resolution SCXRD in order to examine the effect of lanthanide contraction on the coordination geometry in this series of isomorphous compounds consisting of cationic, acetate-bridged, non-linear, one-dimensional coordination polymers of composition [RE(H2O)3(OAc)2]+ and laterally hydrogen bonded halide ions, Hal−. Although the shrinkage of the unit cell volume follows lanthanide contraction very well over the complete range of investigated RE elements, many other parameters (i.e., lattice constants, angles and distances in the RE··· RE alignment, RE-O bond lengths, etc.) exhibit a more complex response on lanthanide contraction often expressed by sigmoid curves that can be ascribed to a continuous transition from CN9 (RE = Ce) to CN8 (RE = Lu) as one acetate group loses the chelate function, an effect accompanied by significant structural changes of the carboxylate group. Therefore, data are best analyzed by use of two subsets represented by the two different structure types of Ce and Lu, the structural features of which change with decreasing/increasing the size of RE3+, up to the borderline between both subsets.

In this present exploration, chitosan doped with different lanthanide oxides such as CeO 2 , Nd 2 O 3 , Sm 2 O 3 , Eu 2 O 3 , Gd 2 O 3 , Dy 2 O 3 and Ho 2 O 3 has been prepared and its optical and thermodynamical properties were studied as a function of the ion size of the lanthanide element and its atomic masses. From the refractive index measurement, the space-filling factor and polarizability have been obtained. The propagation of ultrasonic waves like ultrasonic velocity and its derived quantities such as relaxation strength (r s), adiabatic bulk modulus (K s), acoustic impedance (Z) and adiabatic compressibility (β) have been obtained for different Chitosan-Lanthanide oxides (Ch-LnO). FTIR studies confirm the formation of different Ch-LnO. The variation of all the said properties with ion size is opposite to that of atomic mass due to lanthanide contraction. The results are presented and discussed in a detailed manner. • For the first time, the effect of lanthanide contraction on the optical and thermodynamical properties has been investigated. • There is a competition between size and mass on the said properties has been observed. • All the measured optical and thermodynamical properties are varied with ion size which is in contradiction to atomic mass. [ABSTRACT FROM AUTHOR]

Four new rare-earth metal–organic frameworks containing thieno[3,2b]thiophene-2,5-dicarboxylate (ttdc2−) with general formulae [M2(DMF)4(ttdc)3] (M3+ = Y3+ for 1, La3+ for 2, Tb3+ for 3) and [M2(H2O)2(ttdc)3] (M3+ = Lu3+ for 4) were synthesized. Their crystal structures were determined by performing a single-crystal X-ray diffraction analysis. Coordination polymers 1–3 are based on the binuclear metal-carboxylate building units with the formulae {M2(DMF)4(OOCR)6}. The six-connected blocks in 1–3 form a three-dimensional network with the primitive cubic (pcu) topology. Coordination framework 4 is based on chains comprised by stretched pseudo-binuclear metal-carboxylate building units. The chains are interconnected in four directions with ttdc2− linkers forming the 3D framework. The luminescent properties were studied for the synthesized frameworks in the solid state. All the coordination frameworks show a broad blue emission band (λex = 380 nm) typical for intra-ligand electron transitions. The sensing properties of 3 dispersions in solutions were investigated in detail and the luminescent response (quenching) was discovered in the presence of cinnamaldehyde and quinoline in diluted solutions at concentrations of as low as 4 × 10−1 vol.% and 4 × 10−2 vol.% (~3 × 10−3 M), respectively.

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Crystallochemical analysis with the use of Voronoi–Dirichlet polyhedra (VDPs) has been performed for 711 sulfides, whose structures contain 1199 coordination polyhedra LnSn, where Ln is a lanthanide from La to Lu. It has been established that the sulfides incorporate Ln(II), Ln(III), and Ce(IV) atoms bonding from 6 to 10 sulfur atoms, which exist in the form of S2– or S– ions. The VDP parameters provide the possibility to determine the valence state of Ln atoms in the structures of sulfides and distinguish S2– or S– ions. The VDPs of 2913 sulfur atoms have been characterized to establish the dependence between the multiplicity of S–S bonds and their length. A quantitative estimate of lanthanide contraction in LnIIIXn polyhedra is given depending on the nature of chalcogen Х (O, S, Se, or Te). [ABSTRACT FROM AUTHOR]

Hydrothermal reaction of Ln nitrate and Na2WO4 at pH=8 and 200 °C for 24 hours, in the absence of any additive, has directly produced the scheelite-type sodium lanthanide tungstate of NaLn(WO4)2 for the larger Ln3+ of Ln=La-Dy (including Y, Group I) and an unknown compound that can be transformed into NaLn(WO4)2 by calcination at the low temperature of 600 °C for the smaller Ln3+ of Ln=Ho-Lu (Group II). With the successful synthesis of NaLn(WO4)2 for the full spectrum of Ln, the effects of lanthanide contraction on the structural features, crystal morphology, and IR responses of the compounds were clarified. The temperature- and time-course phase/morphology evolutions and the phase conversion upon calcination were thoroughly studied for the Group I and Group II compounds with Ln=La and Lu for example, respectively. Unknown intermediates were characterized by elemental analysis, IR absorption, thermogravimetry, and differential scanning calorimetry to better understand their chemical composition and coordination. The photoluminescence properties of NaEu(WO4)2 and NaTb(WO4)2, including excitation, emission, fluorescence decay, and quantum efficiency of luminescence, were also comparatively studied for the as-synthesized and calcination products.

The existing range of the centrosymmetric, triclinic RE(OAc)3 · 2AcOH structure type has been extended for RE = Eu and Gd while the structure data of the Nd- and Sm-compounds have been revised and corrected, respectively, using low temperature (T = 100 K), well resolved (2θmax = 56°), highly redundant SCXRD data in order to evaluate the structural evolution within this class of acetic acid solvates by statistical methods. Within the nine-fold mono-capped square-antiprismatic coordination spheres of the RE3+ ions, RE-O distances decrease as a result of lanthanide contraction; some with different rates depending on the coordination modes (2.11/2.21) of the acetate ions. The experimental data show that the internal structural parameters of the acetate ions also correlate with their coordination modes. Both acetic acid molecules act as hydrogen bond donors but only one as monodentate ligand. The geometries of the hydrogen bonds reveal that they are strongly influenced by the size of the rare earth atom. The non-linear, one-dimensional coordination polymer propagates with unequal RE···RE distances along the a-axis. Rods of the coordination polymer are arranged in layers congruently stacked above each other with the hydrogen bonded acetic acid molecules as filler in between. In most cases, data fitting is best described in terms of a quadratic rather than a linear regression analysis.

Two series of new lanthanoid complexes containing 2‐methyl‐8‐quinolinolate (MQ–) have been prepared at elevated temperatures. Lighter elements yield trinuclear complexes [Ln3(MQ)9(HMQ)]·5H2O·3MeOH (1Ln, where Ln = Pr, Eu, Gd, Tb, Dy and Ho) by solvothermal reactions, and heavier lanthanoids yield the mononuclear complexes [Ln(MQ)3(HMQ)]·HMQ·MeOH (2Ln, where Ln = Dy, Ho, Er and Yb), with overlap between the two series found in the cases of Dy and Ho. Magnetic studies reveal that 1Tb, 1Dy, and 2Er show distinct slow magnetic relaxation under external DC fields. The magnetic data for 1Gd yielded the J value for weak antiferromagnetic coupling and the magnetocaloric –ΔSm value of 20 J kg–1 K–1 at 2 K and ΔH = 5 T. [ABSTRACT FROM AUTHOR]

The structures of 272 compounds containing 337 LnTen coordination polyhedra, where Ln is any lanthanide from La to Lu in the crystals, are analyzed using Voronoi–Dirichlet(VD) polyhedra. It is shown that the parameters of VD polyhedra allow determination of the valence state of Ln atoms. It is established that tellurides contain Ln(II) and Ln(III) atoms bonding from 4 to 9 tellurium atoms that exist as Te2–or Tе− ions. The VD polyhedra of Te atoms are determined and it is found that homoatomic Te–Te bonds appear only when there is a deficit of electron donor metal atoms in the composition of crystalline compounds. The dependence of the multiplicity of the Te–Te covalent bond on its length is revealed through the parameters of VD polyhedra. The reliability of this dependence is tested for some compounds, including polytellurides containing 44 networks of tellurium atoms. [ABSTRACT FROM AUTHOR]

Thirteen lanthanide sulfonatoterephthalates, [Ln(TPSO 3 )(H 2 O) 2 ] n (TPSO 3  = sulfonatoterephthalate, C 8 H 3 O 7 S 3− ), with Ln = Ce − Lu, except Pm , as well as [Y(TPSO 3 )(H 2 O) 2 ] n were obtained via hydrothermal syntheses. All materials are isotypic and crystallize in the triclinic crystal system with space group P 1 ¯ . They assemble as two-dimensional (2D) layers that are further tied into three-dimensional (3D) networks via hydrogen bonding. The compounds possess LnO 9 coordination polyhedra, which further assemble as Ln 2 O 16 clusters via edge sharing of two oxygen atoms being supplied by two sulfonato-groups. TPSO 3 -spacers interlink the coordination polyhedra along the b -axis, while carboxylate groups connect adjacent Ln 3+ -ions in the c -direction. The resulting 2D-layers are tied together along the a -axis via hydrogen bonds between coordinated water molecules and two oxygen atoms of the sulfonato-substituents. When plotted versus the ionic radii, the cell parameters, especially the cell volume, show a linear decline between Ce and Tm. We further characterized these materials utilizing elemental analyses, powder X-ray diffraction, and FT-IR spectroscopy. [ABSTRACT FROM AUTHOR]

Bond‐length distributions have been examined for 84 configurations of the lanthanide ions and 22 configurations of the actinide ions bonded to oxygen, for 1317 coordination polyhedra and 10 700 bond distances for the lanthanide ions, and 671 coordination polyhedra and 4754 bond distances for the actinide ions. A linear correlation between mean bond length and coordination number is observed for the trivalent lanthanides ions bonded to O2−. The lanthanide contraction for the trivalent lanthanide ions bonded to O2− is shown to vary as a function of coordination number, and to diminish in scale with an increasing coordination number. The decrease in mean bond length from La3+ to Lu3+ is 0.25 Å for coordination number (CN) 6 (9.8%), 0.22 Å for CN 7 (8.7%), 0.21 Å for CN 8 (8.0%), 0.21 Å for CN 9 (8.2%) and 0.18 Å for CN 10 (6.9%). The crystal chemistry of Np5+ and Np6+ is shown to be very similar to that of U6+ when bonded to O2−, but differs for Np7+. [ABSTRACT FROM AUTHOR]

Hydrothermal reaction of Ln nitrate and Na2WO4 at pH=8 and 200 °C for 24 hours, in the absence of any additive, has directly produced the scheelite-type sodium lanthanide tungstate of NaLn(WO4)2 for the larger Ln3+ of Ln=La-Dy (including Y, Group I) and an unknown compound that can be transformed into NaLn(WO4)2 by calcination at the low temperature of 600 °C for the smaller Ln3+ of Ln=Ho-Lu (Group II). With the successful synthesis of NaLn(WO4)2 for the full spectrum of Ln, the effects of lanthanide contraction on the structural features, crystal morphology, and IR responses of the compounds were clarified. The temperature- and time-course phase/morphology evolutions and the phase conversion upon calcination were thoroughly studied for the Group I and Group II compounds with Ln=La and Lu for example, respectively. Unknown intermediates were characterized by elemental analysis, IR absorption, thermogravimetry, and differential scanning calorimetry to better understand their chemical composition and coordination. The photoluminescence properties of NaEu(WO4)2 and NaTb(WO4)2, including excitation, emission, fluorescence decay, and quantum efficiency of luminescence, were also comparatively studied for the as-synthesized and calcination products. [ABSTRACT FROM AUTHOR]

A series of 3-D lanthanide-transition 3d-4f heterometallic complexes have been synthesized by hydrothermal route from mixtures of 2,2′-bipyridyl-5,5′-dicarboxylic acid (H2bpdc) and acetic acid (HAc) with tetrazoleacetic acid as template. The single-crystal X-ray analysis shows that nine CdLn(H2O)2Cl2(bpdc)Ac complexes (Ln = La for 1, Pr for 2, Nd for 3, Sm for 4, Eu for 5, Gd for 6, Dy for 7, Ho for 8, Er for 9) crystallized in the space group P-1 and featured three-nodal (3, 4, 6)-three connected topological frameworks. The photocatalytic behaviors imply that 1–9 have significant photocatalytic activities for degradation of RhB. [ABSTRACT FROM AUTHOR]

An extended series of trivalent lanthanide 2-nitroterephthalates, [Ln 2 (TPNO 2 ) 3 (H 2 O) 2 ]·2H 2 O, (Ln = Pr through Lu, except Pm) were synthesized hydrothermally from Ln 2 O 3 and 2-nitroterephthalic acid (H 2 TPNO 2 ) at 170 °C in Teflon lined Parr steel autoclaves, and were characterized via single crystal X-ray diffraction, powder X-ray diffraction, FT-IR spectroscopy, elemental analyses, and thermogravimetric analyses. All [Ln 2 (TPNO 2 ) 3 (H 2 O) 2 ]·2H 2 O coordination polymers are isomorphous, crystallizing in the monoclinic crystal system with space group C 2/c. The metal centers in all networks possess the coordination number 8, while forming a three-dimensional extended lattice. Two metal centers form Ln 2 O 14 entities, comprising crystallographically identical LnO 8 polyhedra, connected via edge-sharing, utilizing two carboxylate O-atoms. These Ln 2 O 14 units are separated along the a - and b -axes by individual 2-nitroterephthalate linkers, while being closely connected along the c -axis via two carboxylate groups on each side. Compared to small inorganic anions, the rather flexible 2-nitroterephthalate seems to allow for the unobstructed decrease in size of the LnO 8 polyhedra as Ln 3+ ionic radii decrease towards the heavier Ln elements. Hence, the structural parameters of the crystal lattice adjust gradually without noticeable strain buildup along the series resulting in isomorphous arrangements for all networks. The thermogravimetric and FT-IR measurements seem to confirm the structural features. [ABSTRACT FROM AUTHOR]

Three novel coordination polymers, namely, {[Pr(TTTPC)·(H 2 O) 2 ]·2Cl·NO 3 ·4H 2 O} n ( I ), {[Gd(TTTPC)·(H 2 O) 2 ]·2Cl·NO 3 ·4H 2 O} n ( II ) and {[Yb(TTTPC)·(H 2 O) 2 ]·3Cl·NO 3 ·0.5DMA·6H 2 O} n ( III ) were synthesized in conventional aqueous solutions with H 3 TTTPC ligands (H 3 TTTPC = 1,1′,1″-(2,4,6-trimethylbenzene-1,3,5-triyl(methylene))-tris(pyridine-4-carboxylic acid), DMA = N,N -dimethylacetamide) and characterized by infrared spectrometry and single crystal X-ray diffraction. Experimental results show that these MOFs are isomorphous and isostructural, containing the unit of cavate 14-membered cages (Pr 2 (OCO) 4 ), based on which to generate a one-dimensional (1D) infinite linear metallic chain through the linkage of two COO − groups that are further interlinked reciprocally to polymerize into three-dimensional (3D) porous frameworks. Coordination polymer III shows remarkable selectivity toward Pb 2+ and it can be considered as potential selective luminescent probes for Pb 2+ ion. Additionally, magnetic analysis indicates coordination polymer I presents antiferromagnetism. Besides, lanthanide contraction effect exists in as-synthesized coordination polymers. [ABSTRACT FROM AUTHOR]

The molecular structure of Y, La, and Lu complexes with hemihexaphyrazine ( Нр ), a six-link heteroazaporphyrinoid of АВАВАВ type, has been studied by DFT. It has been found that these MHp (M = Y, La, Lu) complexes have a non-planar structure of C s symmetry with the metal atom dislocated from the center of the cavity to one of the thiadiazole rings. The average lengths of coordination bonds formed by the metal atom with six nitrogen atoms of the thiadiazole moieties are 2.389, 2.566, and 2.358 Å in YHp, LaHp, and LuHp, respectively. Different degrees of deviation from planar structure have been determined in La complex and Y and Lu complexes, characterized by the values of the N N...N N torsion angle between nonequivalent N N bonds in two thiadiazole rings (38.2, 56.0, and 58.6°, respectively). At the same time the internal circumferences of the macrocycle are the same in all three complexes. It has been shown that the planar structures of the complexes of the D 3h symmetry are saddle points on the PES. The transition barriers between the structures of C s and D 3h symmetries have been computed (40.5, 4.6, and 52.4 kJ/mol for YHp, LaHp, and LuHp, respectively). An NBO analysis of the electron density distribution in MHp complexes has been carried out and the nature of coordination bonds in the complexes has been examined. We suppose the coordination bonds in the complexes as three-center ones involving atom M and two nitrogen atoms of N t -N t bond in the thiadiazole moieties, and the Hp ligand as a quasi tridentate one, despite the fact that the metal atom is bonded to six nitrogen atoms of the ligand. The value of the lanthanide contraction Δr Ln (0.208 Å) in the examined LnHp complexes with one ligand has been determined, which turned out to be close to Δr Ln values in the series of lanthanide halogenides with three monovalent ligands and in the series of lanthanide compounds with three bidentate ligands. [ABSTRACT FROM AUTHOR]

The recently developed defective 19-electron half-Heusler (HH) compounds, represented by Nb 1- δ CoSb, possess massive intrinsic vacancies at the cation site and thus intrinsically low lattice thermal conductivity that is desirable for thermoelectric (TE) applications. Yet the TE performance of defective HHs with a maximum figure of merit (zT) <1.0 is still inferior to that of the conventional 18-electron ones. Here, a peak zT exceeding unity is obtained at 1123 K for both Nb 0.7 Ta 0.13 CoSb and Nb 0.6 Ta 0.23 CoSb, using lanthanide contraction as a design factor to select alloying elements that can strongly impede the phonon propagation but weakly disturb the periodic potential. Despite the massive vacancies induced strong point defect scattering of phonons in Nb 0.83 CoSb, using lanthanide contraction as a design factor to select alloying elements that can strongly impede the phonon propagation but weakly disturb the periodic potential. Despite the massive vacancies induced strong point defect scattering of phonons in Nb 0.83 CoSb, Ta alloying is still found effective in suppressing lattice thermal conductivity while maintaining the carrier mobility almost unchanged. In comparison, V alloying significantly deteriorates the carrier transport and thus the TE performance. These results enlarge the category of high-performance HH TE materials beyond the conventional 18-electron ones and highlight the effectiveness of selective scatterings of phonons and electrons in developing TE materials even with massive vacancies., (© 2023 Wiley-VCH GmbH.)

Five isostructural quaternary rare-earth sulfide Mg RE 6 Si 2 S 14 ( RE = Y, Ce, Pr, Nd and Sm) have been successfully synthesized via high-temperature solid-state method. They crystallize in the hexagonal space group P 6 3 and belong to the MnLa 6 Si 2 S 14 structure type. Their 3-D structures are constructed by the connection between infinite 1-D [( RE 6 S 6 ) 6+ ] ∞ tubular and (SiS 4 ) 4– tetrahedron, and Mg 2+ ions occupy the octahedral interspaces in the [( RE 6 S 6 ) 6+ ] ∞ tubular. The lanthanide contraction phenomenon among these compounds is also discussed. Electronic structure calculation indicates that MgY 6 Si 2 S 14 has an indirect optical energy gap of 2.26 eV, and its optical absorption is mainly ascribed to the charge transition from S-3p to Y-4d states. [ABSTRACT FROM AUTHOR]

Hydrothermal reaction of Ln nitrate and Na2WO4at pH=8 and 200 °C for 24 hours, in the absence of any additive, has directly produced the scheelite-type sodium lanthanide tungstate of NaLn(WO4)2for the larger Ln3+of Ln=La-Dy (including Y, Group I) and an unknown compound that can be transformed into NaLn(WO4)2by calcination at the low temperature of 600 °C for the smaller Ln3+of Ln=Ho-Lu (Group II). With the successful synthesis of NaLn(WO4)2for the full spectrum of Ln, the effects of lanthanide contraction on the structural features, crystal morphology, and IR responses of the compounds were clarified. The temperature- and time-course phase/morphology evolutions and the phase conversion upon calcination were thoroughly studied for the Group I and Group II compounds with Ln=La and Lu for example, respectively. Unknown intermediates were characterized by elemental analysis, IR absorption, thermogravimetry, and differential scanning calorimetry to better understand their chemical composition and coordination. The photoluminescence properties of NaEu(WO4)2and NaTb(WO4)2, including excitation, emission, fluorescence decay, and quantum efficiency of luminescence, were also comparatively studied for the as-synthesized and calcination products. [ABSTRACT FROM AUTHOR]

Three new ternary rare-earth zirconium chalcogenides, Ce 2 ZrSe 5 ( 1 ), Pr 2 ZrSe 5 ( 2 ) and Nd 2 ZrSe 5 ( 3 ), have been synthesized by a facile solid-state route with boron as the reducing reagent. They crystallize in the space group Pnma of the orthorhombic system, belonging to the U 3 Se 5 structure type. Their 3-D structures are constructed by parallel polyanionic {[ZrSe 5 ] 6– } n chains and LnSe 8 bicapped trigonal prisms. The magnetic susceptibilities' data indicate their antiferromagnetic-like behavior without magnetic order down to 2 K. The structural relationships among several similar structures are discussed, together with the lanthanide contraction in the Ln 2 ZrSe 5 system. [ABSTRACT FROM AUTHOR]

Three ternary rare-earth zirconium sulfides, Y 2 ZrS 5 ( 1 ), Ce 2 ZrS 5 ( 2 ) and Pr 2 ZrS 5 ( 3 ), have been synthesized by high-temperature solid-state reactions. They crystallize in the space group Pnma of the orthorhombic system, belonging to the Y 2 HfS 5 structure type. There are two types of building units in their structures, RE S 8 bicapped trigonal prisms and ZrS 7 monocapped trigonal prisms. Their structures feature polyanionic {[ZrS 5 ] 6− } n chains and cubane-like {[ RE 4 Zr 2 S 6 ] 8+ } n double chains along the b direction, and RE atoms occupying the polyhedral interspaces between the former chains. The lanthanide contraction phenomenon in the series of RE 2 ZrS 5 ( RE = La–Nd, Sm and Gd) is discussed. The electronic band structure and density of states calculations using Material Studio indicate that the direct optical energy gap of 1 is 1.39 eV and the optical absorption is mainly ascribed to the charge transition from S-3p to Y-4d and Zr-4d states. [ABSTRACT FROM AUTHOR]

The lanthanide contraction is conceptualized traditionally through coordination chemistry. Here we break this mold in a structural study of lanthanide ions dissolved in an amphiphilic liquid. The lanthanide contraction perturbs the weak interactions between molecular aggregates that drive mesoscale assembly and emergent behavior. The weak interactions correlate with lanthanide ion transport properties, suggesting new strategies for rare-earth separation that exploit forces outside of the coordination sphere. [ABSTRACT FROM AUTHOR]