Inorganics

The effects of Ca doping content on the crystal structure, electronic transport, thermal transport, and mechanical properties of In₂O₃ were systematically studied by means of X-ray diffraction (XRD), thermoelectric performance test, and first-principles calculation. XRD analysis shows that Ca²⁺ can be completely solid-dissolved into the In₂O₃ lattice to form a single-phase solid solution without the formation of impurity phases, and the lattice constant increases linearly with the increase in doping content, confirming that Ca²⁺ successfully replaces In³⁺ and triggers lattice expansion. The results of thermoelectric performance tests show that Ca doping can significantly improve the electrical conductivity of the material. The essence is that Ca doping introduces a large number of free electrons through the charge compensation effect, and coordinately regulates the carrier concentration and mobility to optimize the electronic transport performance. In terms of thermal transport performance, Ca doping leads to a decreasing trend of the total thermal conductivity of the material. The core mechanism is that the difference in ionic radius between Ca²⁺ and In³⁺ causes lattice distortion, enhanced mass fluctuation scattering, and defect scattering. At the same time, the decrease in Young’s modulus intensifies phonon scattering, resulting in a significant decrease in lattice thermal conductivity (dominating the change in total thermal conductivity), while the electronic thermal conductivity increases slightly but accounts for a very low proportion. Under the synergistic optimization of electrical and thermal transport, the thermoelectric figure of merit (ZT) of the material increases from ~0.05 to ~0.239, with particularly prominent effects in the medium and high-temperature range.

Copper(II) compounds exhibit interesting magnetic properties due to halide–halide, copper–halide, and intermolecular hydrogen bond interactions. In this study, seven new copper(II) bromide complexes were synthesised, six of which contain Dabco (1,4-diazabicyclo[2.2.2]octane) as a ligand. Single-crystal X-ray diffraction data were refined using both conventional spherical-atom models and a non-spherical-atom approach implemented in NoSpherA2. Magnetic properties were investigated by temperature-dependent magnetic susceptibility and field-dependent magnetisation measurements, analysed using a molecular field approximation. Crystallographic analysis shows that NoSpherA2 significantly improves the description of hydrogen atom positions, yielding C–H and N–H bond lengths closer to neutron diffraction values than conventional refinement. Magnetic measurements indicate that interactions between mononuclear copper(II) centres are determined primarily by the nature of intermolecular exchange pathways rather than copper–copper separations alone. Despite comparable Cu···Cu distances, complexes lacking N–H···Br hydrogen bonds exhibit only weak antiferromagnetic interactions, whereas stronger coupling, effective up to 150 K, is observed when such hydrogen bonds connect neighbouring complexes. These results highlight the importance of hydrogen-bond topology and three-dimensional connectivity in governing magnetic behaviour in mononuclear copper(II) systems.

Graphene-like 2D ZnO (g-ZnO), a wide-bandgap semiconductor, shows great potential for gas sensing, owing to its high surface area and carrier mobility. However, the practical use of it is hampered by its intrinsic chemical inertness. In this study, density functional theory was first used to study the effects of zinc vacancies (V_Zn), oxygen vacancies (V_O), and Au doping on formaldehyde (CH₂O) sensing. The results show that engineering of the defects and the Au doping both significantly improve the reactivity of the material. Specifically, the V_Zn system promotes dissociative chemisorption (E_ads = −5.55 eV) of CH₂O to CO and H atoms. Charge compensation effectively passivates the vacancy states and returns the direct bandgap semiconducting nature of the system. Furthermore, Au doping raises the conduction band and enlarges the bandgap, while the charge accumulation around Au atoms activates the surrounding sites, causing the adsorption mechanism to change from physisorption to chemisorption. Overall, the introduction of V_Zn and Au doping is an efficient way to overcome the surface inertness and improve sensing sensitivity, offering a theoretical framework for the design of high-performance 2D gas sensors.