On the Ytterbium Valence and the Physical Properties in Selected Intermetallic Phases.

The present review summarizes important aspects of the crystal chemistry of ytterbium-based intermetallic compounds along with a selection of their outstanding physical properties. These originate in many cases from the ytterbium valence. Different valence states are possible here, divalent (4f14), intermediate-valent, or trivalent (4f13) ytterbium, resulting in simple diamagnetic, Pauli or Curie-Weiss paramagnetic, or valence fluctuating behavior. Especially, some of the Yb3+ intermetallics have gained deep interest due to their Kondo or heavy Fermion ground states. We have summarized their property investigations using magnetic and transport measurements, specific heat data, NMR, ESR, and Mössbauer spectroscopy, elastic and inelastic neutron scattering, and XAS data as well as detailed thermoelectric measurements.

Searching for Laves Phase Superstructures: Structural and 27Al NMR Spectroscopic Investigations in the Hf-V-Al System.

Laves phases exhibit a plethora of different structures and a multitude of physical properties. Investigations in the ternary system Hf-V-Al led to the discovery of numerous members of the solid solution Hf(V1-xAlx)2, which adopt the hexagonal MgZn2 type (C14) for medium to high amounts of Al (x = 0.2-1) and the cubic MgCu2 type (C15) for small Al amounts (x = 0.05-0.1). While all members exhibit Pauli-paramagnetic behavior due to the absence of localized magnetic moments, the V-rich cubic member Hf(V0.95Al0.05)2 additionally exhibits a superconducting state below TC = 7.6(1) K. All synthesized compounds were characterized by powder X-ray diffraction, and selected samples were furthermore investigated by 27Al solid-state magic-angle spinning (MAS) NMR. HfAl2 exhibits two Al resonances, one rather sharp and one significantly broadened signal, in line with the crystal structure and respective coordination environments. The members of the solid solution exhibit extremely broadened resonances due to the mixing of V and Al on the same crystallographic sites. For nominal Hf(V0.125Al0.875)2, however, two distinct sharp NMR signals were observed. This contrasts with the description of a solid solution. Therefore, single-crystal X-ray studies were conducted, showing that Hf(V0.125Al0.875)2 really is an ordered compound with the sum formula Hf4VAl7 (P3̅m1), which exhibits an, thus far, unknown superstructure of MgZn2.

Oligo-Condensation Reactions of Silanediols with Conservation of Solid-State-Structural Features.

Oligo- and polysiloxanes are usually prepared by condensation reactions in solvents without control of stereochemistry. Here we present a solventless thermal condensation of stable organosilanols. We investigated the condensation reactions of organosilanediols with different organic substituents, having in common at least one aromatic group. The condensation kinetics of the precursors observed by NMR spectroscopy revealed a strong dependence on temperature, time, and substitution pattern at the silicon atom. SEC measurements showed that chain length increases with increasing condensation temperature and time and lower steric demand of the substituents, which also influences the glass transition temperatures (Tg) of the resulting oligo- or polymers. X-ray diffraction studies of the crystalline silanediols and their condensation products revealed a structural correlation between the substituent location in the crystalline precursors and the formed macromolecules induced by the hydrogen bonding pattern. In certain cases, it is possible to carry out topotactic polymerization in the solid-state, which has its origin in the crystal structure.

Self-Assembly of Polymer-Modified FePt Magnetic Nanoparticles and Block Copolymers.

The fabrication of nanocomposites containing magnetic nanoparticles is gaining interest as a model for application in small electronic devices. The self-assembly of block copolymers (BCPs) makes these materials ideal for use as a soft matrix to support the structural ordering of the nanoparticles. In this work, a high-molecular-weight polystyrene-b-poly(methyl methacrylate) block copolymer (PS-b-PMMA) was synthesized through anionic polymerization. The influence of the addition of different ratios of PMMA-coated FePt nanoparticles (NPs) on the self-assembled morphology was investigated using transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). The self-assembly of the NPs inside the PMMA phase at low particle concentrations was analyzed statistically, and the negative effect of higher particle ratios on the lamellar BCP morphology became visible. The placement of the NPs inside the PMMA phase was also compared to theoretical descriptions. The magnetic addressability of the FePt nanoparticles inside the nanocomposite films was finally analyzed using bimodal magnetic force microscopy and proved the magnetic nature of the nanoparticles inside the microphase-separated BCP films.

Polycobaltoceniumylmethylene - A Water-Soluble Polyelectrolyte Prepared by Ring-Opening Transmetalation Polymerization.

The synthesis of a water-soluble polycobaltoceniumylmethylene chloride (PCM-Cl) via ring-opening transmetalation polymerization is presented. Starting from a carba[1]magnesocenophane and cobalt(II) chloride, this route gives access to a polymer with methylene-bridged cobaltocenium moieties within the polymers' main-chain. The polymer was characterized by NMR spectroscopy, elemental analysis, TGA, DSC, XRD, and CV measurements, as well as UV-vis spectroscopy. Furthermore, GPC measurements in an aqueous eluent versus pullulan standards were conducted to gain insight into the obtained molar masses and distributions. In addition, the ion-dependent solubility was demonstrated by anion exchange, tuning the hydrophobic/hydrophilic properties of this redox-responsive material.

Formation of the Sub-oxide Sc4Au2O1-x and the Drastically Negative 27Al NMR Shift in Sc2Al.

During attempts to synthesize Sc4AuAl in the cubic Gd4RhIn-type structure, the solid solution Sc2Au0.5Al0.5 in the PbCl2-type structure formed instead. Subsequently, the solid solution Sc2Au1-xAlx was investigated with respect to its existence range along with the structure types formed for different compositions with x = 0, 0.25, 0.5, 0.75, and 1. According to X-ray powder diffraction studies, Sc2Al and nominal Sc2Au0.25Al0.75 crystallized in the hexagonal Ni2In-type structure (P63/mmc), while Sc2Au0.5Al0.5, Sc2Au0.75Al0.25, and Sc2Au were found to crystallize in the orthorhombic PbCl2-type structure (Pnma). The crystal structures of Sc2Au and Sc2Au0.59(1)Al0.41(1) were refined from single-crystal data (Sc2Au: a = 648.0(1), b = 467.2(1), c = 835.2(2) pm, wR2 = 0.0382, 535 F2 values, 25 variables; Sc2Au0.59(1)Al0.41(1): a = 632.48(5), b = 472.16(3), c = 848.67(6) pm, wR2 = 0.0484, 540 F2 values, 21 variables). Contamination with air during the synthesis of Sc2Au led to the discovery of a compound adopting the cubic W4Co2C-type structure (stuffed cubic Ti2Ni type). Using Sc2O3 as a defined oxygen source led to samples with high amounts of Sc4Au2O1-x. All intermetallic compounds exhibited Pauli paramagnetic behavior in the investigated temperature range of 2.1 to 300 K, and no superconductivity was observed at low temperatures and low fields. Sc2Au and Sc2Al were investigated by 27Al and 45Sc solid-state NMR investigations. For Sc2Al, one signal was found in the 27Al NMR spectra in line with the crystal structure; however, an extremely negative resonance shift of δ = -673 ppm was observed. In both compounds, two Sc resonances were observed, in line with the proposed crystal structure. Finally, it was observed that the stability of Sc2Au in air is limited. This was investigated via thermal analysis and (temperature-dependent) powder X-ray diffraction. DFT calculations helped in assessing charge analysis, electronic properties, and chemical bonding.

Theoretical and 27Al NMR Spectroscopic Investigations of Binary Intermetallic Alkaline-Earth Aluminides.

The binary alkaline-earth aluminides AEAl2 (AE = Ca and Sr) and AEAl4 (AE = Ca-Ba) have been synthesized from the elements and investigated via powder X-ray diffraction experiments. CaAl2 adopts the cubic MgCu2-type structure (Fd3̅m), while SrAl2 crystallizes in the orthorhombic KHg2-type (Imma). LT-CaAl4 crystallizes with the monoclinic CaGa4-type (C2/m), while HT-CaAl4, SrAl4, and BaAl4 adopt the tetragonal BaAl4-type structure (I4/mmm). The close structural relation of the two CaAl4 polymorphs was established using a group-subgroup relation in the Bärnighausen formalism. In addition to the room-temperature and normal pressure phase of SrAl2, a high-pressure/high-temperature phase has been prepared using multianvil techniques, and its structural and spectroscopic parameters were determined. Elemental analysis by inductively coupled plasma mass spectrometry showed that no significant impurities with other elements besides the weighed ones are present and the chemical compositions match the synthesized ones. The title compounds have been furthermore investigated by 27Al solid-state magic angle spinning NMR experiments to validate the crystal structure and to gain information about the influence of the composition on the electron transfer and the NMR characteristics. This has also been investigated from a quantum chemical point of view using Bader charges, while the stabilities of the binary compounds in the three phase diagrams (Ca-Al, Sr-Al and Ba-Al) have been studied by calculations of formation energies per atom.

Raman and NMR spectroscopic and theoretical investigations of the cubic laves-phases REAl2 (RE = Sc, Y, La, Yb, Lu).

The cubic Laves-phase aluminides REAl2 with RE = Sc, Y, La, Yb and Lu were prepared from the elements by arc-melting or using refractory metal ampoules and induction heating. They all crystallize in the cubic crystal system with space group Fd3̄m and adopt the MgCu2 type structure. The title compounds were characterized by powder X-ray diffraction and spectroscopically investigated using Raman and 27Al and in the case of ScAl2 by 45Sc solid-state MAS NMR. In both, the Raman and NMR spectra, the aluminides exhibit only one signal due to the crystal structure. DFT calculations were used to calculate Bader charges illustrating the charge transfer in these compounds along with NMR parameters and densities of states. Finally, the bonding situation was assessed by means of ELF calculations rendering these compounds aluminides with positively charged REδ+ cations embedded in an [Al2]δ- polyanion.

Black Titania and Niobia within Ten Minutes - Mechanochemical Reduction of Metal Oxides with Alkali Metal Hydrides.

Partially or fully reduced transition metal oxides show extraordinary electronic and catalytic properties but are usually prepared by high temperature reduction reactions. This study reports the systematic investigation of the fast mechanochemical reduction of rutile-type TiO2 and H-Nb2 O5 to their partially reduced black counterparts applying NaH and LiH as reducing agents. Milling time and oxide to reducing agent ratio show a large influence on the final amount of reduced metal ions in the materials. For both oxides LiH shows a higher reducing potential than NaH. An intercalation of Li+ into the structure of the oxides was proven by PXRD and subsequent Rietveld refinements as well as 6 Li solid-state NMR spectroscopy. The products showed a decreased band gap and the presence of unpaired electrons as observed by EPR spectroscopy, proving the successful reduction of Ti4+ and Nb5+ . Furthermore, the developed material exhibits a significantly enhanced photocatalytic performance towards the degradation of methylene blue compared to the pristine oxides. The presented method is a general, time efficient and simple method to obtain reduced transition metal oxides.

Self-Activation of Inorganic-Organic Hybrids Derived through Continuous Synthesis of Polyoxomolybdate and para-Phenylenediamine Enables Very High Lithium-Ion Storage Capacity.

Inorganic-organic hybrid materials with redox-active components were prepared by an aqueous precipitation reaction of ammonium heptamolybdate (AHM) with para-phenylenediamine (PPD). A scalable and low-energy continuous wet chemical synthesis process, known as the microjet process, was used to prepare particles with large surface area in the submicrometer range with high purity and reproducibility on a large scale. Two different crystalline hybrid products were formed depending on the ratio of molybdate to organic ligand and pH. A ratio of para-phenylenediamine to ammonium heptamolybdate from 1 : 1 to 5 : 1 resulted in the compound [C6 H10 N2 ]2 [Mo8 O26 ] ⋅ 6 H2 O, while higher PPD ratios from 9 : 1 to 30 : 1 yielded a composition of [C6 H9 N2 ]4 [NH4 ]2 [Mo7 O24 ] ⋅ 3 H2 O. The electrochemical behavior of the two products was tested in a battery cell environment. Only the second of the two hybrid materials showed an exceptionally high capacity of 1084 mAh g-1 at 100 mA g-1 after 150 cycles. The maximum capacity was reached after an induction phase, which can be explained by a combination of a conversion reaction with lithium to Li2 MoO4 and an additional in situ polymerization of PPD. The final hybrid material is a promising material for lithium-ion battery (LIB) applications.

An Anionic Amido-Substituted Seven-Vertex Siliconoid Cluster.

The silanide [Si4 {N(SiMe3 )Dipp}3 ]- (1) transforms into the anionic siliconoid cluster [Si7 {N(SiMe3 )Dipp}3 ]- (2) with four unsubstituted silicon atoms as a contact ion pair with [K([18]crown-6)] in C6 D6 at room temperature within five weeks. Anion 2 was investigated by natural population analysis and visualization of intrinsic atomic orbitals. Magnetically induced current-density calculations of 2 revealed two distinct strong diatropic vortices that sum up in one direction and create a strongly shielded apical silicon atom in 2.

Triangular Arrangement of Ferromagnetic Iron Chains in the High-TC Ferromagnet TiFe1-x Os2+x B2.

Transition-metal borides (TMBs) containing Bn -fragment (n>3) have recently gained interest for their ability to enable exciting magnetic materials. Herein, we show that the B4 -containing TiFe0.64(1) Os2.36(1) B2 is a new ferromagnetic TMB with a Curie temperature of 523(2) K and a Weiss constant of 554(3) K, originating from the chain of M3 -triangles (M=64 %Fe+36 %Os). The new phase was synthesized from the elements by arc-melting, and its structure was elucidated by single-crystal X-ray diffraction. It belongs to the Ti1+x Os2-x RuB2 -type structure (space group P 6 ‾ 2 m, no. 189) and contains trigonal-planar B4 boron fragments [B-B distance of 1.87(4) Å] interacting with M3 -triangles [M-M distances of 2.637(8) Šand 3.0199(2) Å]. The experimental results were supported by computational calculations based on the ideal TiFeOs2 B2 composition, which revealed strong ferromagnetic interactions within and between the Fe3 -triangles. This discovery represents the first magnetically ordered Os-rich TMB, thus it will help expand our knowledge of the role of Os in low-dimensional magnetism of intermetallics and enable the design of such materials in the future.

Polymorphism and optical, magnetic and thermal properties of the either phyllo- or inosilicate-analogous borosulfate Cu[B2(SO4)4].

Two polymorphs of the borosulfate Cu[B2(SO4)4] can be selectively prepared by solvothermal syntheses. The crystal structures of inosilicate-analogous α-Cu[B2(SO4)4] (P1̄, no. 2, a = 5.2636(2), b = 7.1449(2), c = 7.9352(2) Å, α = 73.698(2)°, ß = 70.737(2)°, γ = 86.677(2)°, 65 parameters, RBragg = 0.0052) and the new phyllosilicate-analogous polymorph ß-Cu[B2(SO4)4] (P21/n, no. 14, a = 7.712(3), b = 8.149(3), c = 9.092(3) Å, ß = 111.22(1)°, 3829 independent reflections, 106 parameters, wR2 = 0.054) are discussed. Further, the optical, magnetic and thermal properties of both polymorphs are investigated with focus on the role of the Cu2+ cation and its Jahn-Teller effect. The findings are confirmed by DFT calculations yielding insights in the stability of the synthesised polymorphs as well as a predicted γ-modification. Additionally, the crystal structures of two polymorphs of copper hydrogensulfate Cu(HSO4)2-I (P21/n, no. 14, a = 4.7530(2), b = 8.5325(4), c = 7.3719(3) Å, ß = 100.063(1)°, 1063 independent reflections, 55 parameters, wR2 = 0.052) and Cu(HSO4)2-II (P1̄, no. 2, a = 4.79.88(8), b = 7.857(1), c = 8.057(1) Å, α = 77.86(1)°, ß = 87.02(1)°, γ = 89.82(1)°, 1044 independent reflections, 109 parameters, wR2 = 0.132) as well as that of Cu[S2O7] (C2/c, no. 15, a = 6.6341(4), b = 8.7302(5), c = 9.0555(8) Å, ß = 104.763(3)°, 1117 independent reflections, 48 parameters, wR2 = 0.049) are presented and the cyclosilicate-analogous borosulfate Cu[B(SO4)2(HSO4)] is fully characterised with respect to its optical and thermal properties.

Porous Mixed-Metal Oxide Li-Ion Battery Electrodes by Shear-Induced Co-assembly of Precursors and Tailored Polymer Particles.

Due to their various applications, metal oxides are of high interest for fundamental research and commercial usage. Per applications as catalysts or electrochemical devices, the tailored design of metal oxides featuring a high specific surface area and additional functionalities is of the utmost importance for the performance of the resulting materials. We report a new method for preparing free-standing films consisting of hierarchically porous metal oxides (titanium and niobium based) by combining emulsion polymerization and shear-induced monodisperse particle self-assembly in the presence of sol-gel precursors. After thermal treatment, the resulting porous materials can be used as electrodes in Li-ion batteries. The titanium and niobium sol-gel precursors were partially immobilized to the surface of organic core-interlayer particles featuring hydroxyl groups to obtain hybrid organic-inorganic particles through the melt-shear organization process. Free-standing particle-based films, in analogy to elastomeric opal films and colloidal crystals, can be prepared in a convenient one-step preparation process. After thermal treatment, ordered pores are obtained, while the pristine metal oxide precursor shell can be converted to the (mixed) metal oxide matrix. Heat treatment under CO2 leads to mixed-TiNb oxide/carbon hybrid materials. The highly porous derivative structure enhances electrolyte permeation. When tested as Li-ion battery electrodes, it shows a specific capacity of 335 mAh·g-1 at a rate of 10 mA·g-1. After 1000 cycles at 250 mA·g-1, the electrodes still provided a specific capacity of 191 mAh·g-1.

Rare-Earth-Free Magnets: Enhancing Magnetic Anisotropy and Spin Exchange Toward High-TC Hf2MIr5B2 (M = Mn, Fe).

Designing new rare-earth-free (REF) permanent magnetic materials (PMM) to replace the high performing but critically restrained rare-earth-based PMM remains a great challenge to the scientific community. Here, we report on the rational design of new REF PMM, Hf2MIr5B2 (M = Fe, Mn) via a theory-experiment combined approach. Density functional theory (DFT) predicted strong interchain M-M spin-exchange coupling and large magnetocrystalline anisotropy energies (EMAE) for the new compounds, suggesting potential intrinsic PMM properties. Subsequent experimental bulk syntheses and magnetic characterizations established the highest ordering temperature (TC ∼ 900 K) for Hf2FeIr5B2 and the highest intrinsic coercivity (HC) value for Hf2MnIr5B2 (HC = 62.1 kA/m) reported to date for Ti3Co5B2-type compounds. Importantly, at room temperature both phases show significant coercivities due to intrinsic factors only, hinting at their huge potential to create REF PMM by improving extrinsic factors such as controlling the microstructure and the domain orientation.

Cu2ZnSbS4: A Thioantimonate(V) with Remarkably Strong Covalent Sb-S Bonding.

A new member to the A2IBIICIVX4 compound family, Cu2ZnSbS4, was synthesized successfully using ball milling and postannealing in H2S-atmosphere. For comparative purposes, Cu3SbS4 was additionally prepared using the same synthetic approach. As is common for A2IBIICIVX4 compounds, Cu2ZnSbS4 crystallizes isostructural to Cu3SbS4 in the stannite-type structure in space group I42m. Both antimony sulfides contain monovalent diamagnetic copper and are characterized by substantial covalent bonding. This is consistent with the 121Sb isomer shifts occurring for the Mössbauer spectra of Cu2ZnSbS4 (-7.71 mm s-1) and Cu3SbS4 (-7.68 mm s-1) which fall in the region of covalently bonded Sb(V) compounds. These spectroscopic results are supported by electronic structure calculations.

Ni[B2 (SO4 )4 ] and Co[B2 (SO4 )4 ]: Unveiling Systematic Trends in Phyllosilicate Analogue Borosulfates.

Borosulfates are compounds analogous to silicates, with heteropolyanionic subunits of vertex-linked (SO4 )- and (BO4 )-tetrahedra. In contrast to the immense structural diversity of silicates, the number of borosulfates is yet very limited and the extent of their properties is still unknown. This is particularly true for representatives with phyllosilicate and tectosilicate analogue anionic substructures. Herein, we present Ni[B2 (SO4 )4 ] and Co[B2 (SO4 )4 ], two new borosulfates with phyllosilicate analogue topology. While the anionic subunits of both structures are homeotypic, the positions of the charge compensating cations differ significantly: NiII is located between the borosulfate layers, while CoII -in contrast-is embedded within the layer. Detailed analysis of these two structures based on single-crystal X-ray diffraction, magnetochemical investigations, X-ray photoelectron spectroscopy, and quantum chemical calculations, unveiled the reasons for this finding. By in silico comparison with other divalent borosulfates, we uncovered systematic trends for phyllosilicate analogues leading to the prediction of new species.

On the phosphors Na5M(WO4)4 (M = Y, La-Nd, Sm-Lu, Bi) - crystal structures, thermal decomposition, and optical and magnetic properties.

The pentasodium rare-earth tungstates Na5M(WO4)4 are closely related to the sodium rare-earth double tungstates Na5M(WO4)2 both adopting the scheelite structure type (space group I41/a, no. 88). After the preparation of polycrystalline powders via flux syntheses improving the phase purity significantly, the crystal structures of Na5M(WO4)4 (M = Y, La-Nd, Sm-Lu, Bi) were determined by single crystal XRD and Rietveld analysis. Na5M(WO4)4 is a promising phosphor material both as a host and as a 100% phosphor due to the possible charge transfer of the tungstate group and the absence of any concentration quenching. Na5M(WO4)4 incongruently melts to Na5M(WO4)2 and Na2WO4. After the clarification of the crystallographic relationship of Na5M(WO4)4 and Na5M(WO4)2 based on a rare isomorphic transition of index 5 (i5) the non-linear trend of the decomposition temperature within the row of rare earth ions is explained systematically taking into account the existence of domains within the crystal structure predetermining the posterior decomposition. A miscibility gap for solid solutions of Na5Y(WO4)4 and Na5Eu(WO4)4 or Na5Tb(WO4)4 is identified and its temperature dependence is investigated. Furthermore, the investigation of the fluorescent properties of Na5M(WO4)4 (M = Pr, Sm, Eu, Tb, Tm, Bi), Na5Y1-xEux(WO4)4 and Na5Y1-yTby(WO4)4 provided insights into the weak ligand field and the energy transfer from WO42- to M3+ governed by the emission of the sensitiser within Na5M(WO4)4. Additionally, the compounds were characterised by magnetic measurements and vibrational, UV/Vis and 151Eu Mössbauer spectroscopy.

On the formation of the Gd3Ru4Al12versus the Y2Co3Ga9 type structure - M3Rh4Al12 (M = Ca, Eu) versus M2T3Al9 (M = Ca, Sr, Eu, Yb; T = Ir, Pt).

The new Y2Co3Ga9 and Gd3Ru4Al12 type representatives M2T3Al9 (M = Ca, Sr, Eu; T = Ir, Pt) and M3Rh4Al12 (M = Ca, Eu) have been synthesized from the elements by heating the respective elemental compositions in sealed tantalum tubes. The samples were analysed by powder X-ray diffraction to check their purity. By applying different temperature treatments, their phase purity and crystallinity were enhanced. The crystal structures of Ca3Rh4Al12 and Eu3Rh4Al12 (hexagonal Gd3Ru4Al12 type, P63/mmc) as well as Ca2Ir3Al9 and Ca2Pt3Al9 (orthorhombic Y2Co3Ga3 type, Cmcm) were refined from single-crystal X-ray diffraction data. All structures can be described based on distorted cube-like T@Al8 units that are connected to form strands. Additionally, an Al11 supertetrahedral building block can be identified within the structures. While the trigonal bipyramidal core of the cluster contains substantial bonding interactions in the case of the M3Rh4Al12 members, the connection via common edges in the case of the M2Ir3Al9 compounds seems to weaken these interactions. The differences in the bonding situation and the question why these different structure types are formed for the different transition metals has been targeted by quantum-chemical calculations. The calculated formation energy using three different reaction paths suggests that the stability of these phases is highly dependent on the side phases involved, even though Ca3T4Al12 phases are in general thermodynamically more favourable. According to the Bader analysis of the two polyanions, an improved covalent bonding can be observed in the [T4Al12]δ- over the [T3Al9]δ- framework.

Physical and Magnetocaloric Properties of TbPdAl2 and the Ferromagnetic Solid Solution Tb1-xLuxPdAl2 (x = 0.1-0.9).

TbPdAl2 and the solid solution Tb1-xLuxPdAl2 (x = 0.1-1) have been synthesized via arc-melting techniques using the elements as starting materials and crystallize in the orthorhombic MgCuAl2-type structure (Cmcm). As expected, the unit cell volumes decrease due to the lanthanide contraction from the Tb to Lu compounds, thus showing Vegard behavior because of the differences of the ionic radii of the trivalent rare-earth cations. TbPdAl2 orders ferromagnetically below TC = 85.5(5) K and shows partial magnetic saturation already at low fields. The magnetic phase transition has been additionally investigated by heat capacity measurements, showing a broadened λ anomaly at THC = 83.2(1) K. The electrical resistivity is almost linear above TC, indicating dominant electron-phonon interactions. Below the ordering temperature, electron-spin wave scattering with a ρ ∼ T2 behavior is evident. In the solid solution Tb1-xLuxPdAl2 (x = 0-1), the ferromagnetic Curie temperatures decrease in a linear fashion with increasing Lu content. Investigations of the magnetocaloric properties of TbPdAl2 obtained a maximum magnetic entropy change of -ΔSMmax = 1.2, 2.2, 3.1, and 3.6 J kg-1 K-1 for the field changes of ΔH = 10, 20, 50, and 70 kOe, respectively. The rather low values are caused by entropy losses due to hysteresis behavior. The relative cooling power for TbPdAl2, therefore, also exhibits comparably low values of 32, 81, 142, and 178 J kg-1.