Lead-free double perovskite Cs₂AgSbBr₆ is synthesized to show a low indirect bandgap of 1.64 eV.

A combination of gas adsorption and gas breakthrough measurements show that the metal-organic framework, Al(HCOO) ₃ (ALF), which can be made inexpensively from commodity chemicals, exhibits excellent CO ₂ adsorption capacities and outstanding CO ₂ /N ₂ selectivity that enable it to remove CO ₂ from dried CO ₂ -containing gas streams at elevated temperatures (323 kelvin). Notably, ALF is scalable, readily pelletized, stable to SO ₂ and NO, and simple to regenerate. Density functional theory calculations and in situ neutron diffraction studies reveal that the preferential adsorption of CO ₂ is a size-selective separation that depends on the subtle difference between the kinetic diameters of CO ₂ and N ₂ . The findings are supported by additional measurements, including Fourier transform infrared spectroscopy, thermogravimetric analysis, and variable temperature powder and single-crystal x-ray diffraction.

GeTe is highly sought-after due to its versatility as a high-performance thermoelectric material and phase change material, as well as a ferroelectric Rashba semiconductor. Compared to most thermoelectric materials, it has an additional degree of freedom of rhombohedral–cubic phase transition at 673 K. At this temperature, the lattice thermal conductivity approaches a theoretical minimum due to ferroelectric instability while the high-energy Σ and low-energy L bands converge to give outstanding electronic properties. Therefore, modulation of the phase transition temperature allows simultaneous and synergistic tuning of the electronic and thermal transport properties to achieve high zT. In this work, Sn alloying together with Bi,Sb doping is used to suppress the phase transition to achieve a pure cubic structure with a lattice thermal conductivity of around 0.4 W m⁻¹ K⁻¹ and peak zT of 1.7 at 723 K with an average zT of 1.23 between 400 and 800 K. Furthermore, the Vickers hardness of 270 and Young's modulus of 63.5 GPa in Ge_0.4Sn_0.4Bi_0.02Sb_0.12Te are by far the highest amongst binary chalcogenides. More importantly, the high quality factor achieved in this work gives ample room for further zT improvements. The fundamental insights drawn from this work provide a pathway towards engineering GeTe-based alloys to achieve high zT at any temperature of interest.

Two hybrid rare-earth double perovskites, (CH₃NH₃)₂KGdCl₆ and (CH₃NH₃)₂KYCl₆, have been synthesized by a solution evaporation method and their structures determined by variable temperature single-crystal X-ray diffraction. The diffraction results show that at room temperature both perovskites adopt a rhombohedral structure with R3̅m symmetry, as found previously for (MA)₂KBiCl₆, and lattice parameters of a = 7.7704(5) Å and c = 20.945(2) Å for (MA)₂KGdCl₆ and a = 7.6212(12) Å and c = 20.742(4) Å for (MA)₂KYCl₆. Both phases exhibit a rhombohedral-to-cubic phase transition on heating to ∼435 K for (MA)₂KYCl₆ and ∼375 K for (MA)₂KGdCl₆. Density functional calculations on the rhombohedral phase indicate that both materials have large direct band gaps, are mechanically stable, and, in the case of (MA)₂KGdCl₆, could exhibit magnetic ordering at low temperatures.