SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-026-4494-9
Superionic conductors exhibit high cation mobility arising from weak binding and continuous transport pathways, atomistically characterized by extensive structural disorder and partial occupancy akin to amorphization. This disorder, whether confined to a cation sublattice or extended to full amorphization, strongly impedes lattice thermal transport, rendering these materials intrinsically ideal thermal insulators. This work investigates Ag26I18W4O16, a superionic conductor tunable from fully amorphous to single-crystalline states, as a model system to probe the impact of disorder and amorphization on thermal transport. Extensive Ag+ disorder, in both crystalline and amorphous phases, reduces thermal conductivity to approximately the theoretical lower bound of 0.16 W/m-K with virtually no temperature dependence, while concurrently achieving the lowest mean sound velocity ever recorded for a dense solid. Pair distribution function (PDF) analysis of synchrotron X-ray total scattering data indicates that short-range disorder (< 5 Å), rather than long-range periodicity, governs thermal insulation performance in both phases. These findings suggest a design strategy reconciling structural stability with glass-like thermal insulation.
SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-026-4290-9
Thermoelectric materials enable direct and reversible conversion between heat and electricity, offering unique advantages for waste heat recovery, solid-state refrigeration, and deep-space power systems. The performance is evaluated by the dimensionless figure of merit, zT = S²σT/κ, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature, and κ is the total thermal conductivity. Achieving high zT requires simultaneous realization of a large power factor (S²σ) and low thermal conductivity. However, these parameters are intrinsically coupled, posing a fundamental challenge. PbTe is a representative thermoelectric material operating in the intermediate temperature range, with outstanding performance originating from its unique electronic band structure featuring multiple nearly degenerate valence band maxima near the L points. Band convergence via alloying with mono-tellurides such as MgTe, MnTe, CdTe, YbTe, SrTe, and EuTe effectively modifies the valence band structure, increasing band degeneracy and density-of-states effective mass, thereby enhancing electrical conductivity without decreasing the Seebeck coefficient. However, increasing the content of these mono-tellurides limits acceptor dopability, making conventional dopants like Na difficult to incorporate. This study demonstrates that co-doping strategies can preserve dopability while achieving band convergence and dislocation engineering, leading to significantly reduced lattice thermal conductivity and extraordinary peak zT values. The decoupling of electronic and thermal transport through this approach offers a promising route for high-performance thermoelectrics.
SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-025-3972-9
SnTe-based thermoelectric materials have demonstrated significant improvements in performance and are considered a promising, less-toxic alternative to PbTe. However, a substantial gap persists between experimental device efficiencies and those predicted from material performance metrics, primarily due to extra resistance in the contact layers. To fully realize the potential of SnTe thermoelectrics at the device level, it is critical to develop contact layers that ensure strong interfacial bonding, high thermal stability, and low electrical contact resistance. Although Ni is the most commonly used contact material for SnTe devices, it exhibits significant interdiffusion with SnTe, which can degrade interfacial integrity and ultimately lead to long-term device failure. Here, a reliable contact layer for SnTe through thermodynamic analysis of the SnTe-Ni3Te2 phase diagram is identified, Ni5.75SnTe5 selected as a promising candidate. A single-leg thermoelectric device based on Sn0.96Bi0.04Te0.98Se0.02 with Ni5.75SnTe5 as a contact layer is fabricated, achieving a contact resistivity of approximately 3.7 μΩ cm2. This contact layer selection strategy shows great promise for application to other thermoelectric materials.