P-type PbTe is one of the most representative high-performance thermoelectric materials, while the conversion efficiency of the fabricated module is limited by the relatively low zT of n-type PbTe. Here, we report the optimization of Cu-doped n-type PbTe by tuning the ionic migration energy, aiming for the high-efficiency and robust modules. It is revealed that the strategy of lattice contraction, achieved by Ge/Se co-doping, preserves the excellent carrier mobility from interstitial Cu and suppresses the unstable transport at high temperature. In the optimized sample of Pb_0.94Ge_0.06Cu_0.02Se_0.04Te_0.96, a superior average zT (300–823 K) of 1.04 and a high peak zT of 1.45 at 823 K are obtained. A remarkable conversion efficiency of 10.5% at a temperature difference of 500 K is achieved in the fabricated PbTe-based module.

Cobalt oxide, as one of the most fascinating examples of correlated electronic system, exhibits several exotic transport characteristics, such as superconductivity, charge ordering, and topological frustration. In this study, we are reporting the observation of another intriguing transport phenomenon in calcium cobaltates. Specifically, under a large magnetic field of 7 T, we observed an anomalously enhanced thermal conductivity that was accompanied with a largely suppressed thermopower. This observation reveals a hitherto undiscovered correlation between the two transport factors. Within the premise of Heisenberg model, we have shown that the observed experimental results can be explained consistently only if the magnon excitation is taken into account. Our study offers an insight into the puzzling origin of large thermopower observed in layered cobaltates and provides a specific strategy for further optimization of thermopower.

A series of Y_2.985Al_5-xGa_xO₁₂:0.015Ce (YAGG:Ce, x = 0, 1, 2, 3, 4, 5) transparent ceramics were prepared via a solid-state reaction method. Two-step sintering technique was proved to be an effective approach to prepare functional ceramics with high Ga concentration, and Y₃Ga₅O₁₂ (YGG) transparent ceramic was successfully prepared for the first time. According to the variation of Al/Ga ratio, regulation of band structure and luminescence properties of YAGG:Ce transparent ceramics were effectively investigated. When Ga substitutes Al sites, the tetrahedral site is more favorable compared to the octahedral site for Ga to occupy according to the first-principle calculation. A continuous blue shift of the emission from 565 to 515 nm was achieved as Ga was gradually introduced into Y₃Al₅O₁₂:Ce matrix. High quality green light was obtained by coupling the YAGG:Ce ceramics with commercial blue InGaN chips. Transparent luminescence ceramics accomplished in this work can be quite prospective for high power LED application.