Grain size optimization for high-performance polycrystalline SnSe thermoelectrics

Grain size significantly affects the thermoelectric performance, the thickness of oxidized/amorphous layer and the stability of SnSe polycrystals. As a result, sample Sn0.97Na0.03Se with average grain size around 4 μm achieves a high thermoelectric performance and stability in the whole measured temperature range.

High-Temperature Acoustical and Electrical Properties of LGS, LGT and CTGS Resonators

Acoustic characteristics and electrical conductivity of CTGS, LGT and LGS bulk acoustic wave resonators operated at the fundamental mode in the temperature range of 20-1470°C are studied. It is shown that LGS and CTGS resonators can be excited piezoelectrically up to 1470 and 1270°C, respectively, which is close to their melting temperatures. The electrical conductivity of CTGS is found to be by at least two and three orders of magnitude lower than that of LGS and LGT, respectively, over the temperature range 400-1000°C. Measurements of temperature dependent electromechanical losses show, that they are at least by two orders of magnitude lower in CTGS comparing to that in LGS within the measured temperature range.

Thermoelectric Properties of the Nanostructured NaPb18-xSnxMTe20 (M=Sb, Bi) Materials

The thermoelectric properties of materials with compositions NaPb18-xSnxMTe20 (M=Sb, Bi, x=0, 3, 5, 9, 13, 16 and 18) were investigated in the temperature range 300-670K. All compositions exhibited p-type behavior over the measured temperature range. Electronic properties and transport were tuned through the manipulation of the Pb/Sn ratio. Increasing the Sn fraction results in an increase in electrical conductivity and a decrease in thermopower. The compositions NaPb13Sn5SbTe20 and NaPb9Sn9SbTe20 show a lattice thermal conductivity of ∼1 W/m/K at room temperature.

Thermoelectric Properties of Doped Iron Disilicide

ABSTRACTIn order to investigate the thermoelectric properties of Re-doped β-FeSi2 (Fe1-xRexSi2), Ir-doped β-FeSi2 (Fe1-xIrxSi2), and Pt-doped β-FeSi2 (Fe1-xPtxSi2), the electrical resistivity, the Seebeck coefficient, and the thermal conductivity of these samples have been measured in the temperature range between 300 and 1150 K. Fe1-xRexSi2 is p-type, while Fe1-xIrxSi2 and Fe1-xPt xSi2 are n-type over the measured temperature range. The solubility limits of dopant are estimated to be 0.2at% for Fe1-xRexSi2, 0.5at% for Fe1-xIrxSi2, and 1.9at% for Fe1-xPtxSi2. A maximum ZT value of 0.14 was obtained for Fe1-xPt xSi2 (x=0.03) at the temperature 847 K.

Diffusion of Sr in Bi2Sr2Can–1CunO2n+4

Tracer diffusion of 85Sr in polycrystalline Bi2Sr2Can-1CunO2n+4 has been investigated for n = 1, 2, and 3 in an oxygen atmosphere between 775 and 850 °C. A radiotracer serial-sectioning technique was used to measure the concentration profiles, which were fit to a solution of the diffusion equation to calculate the diffusivities. The activation energies were 403, 553, and 519 kJ/mole, for n = 1, 2, and 3, respectively. However, the absolute values of D for the various layered superconductors did not differ by more than an order of magnitude over the measured temperature range. The diffusivity of Sr at 800 °C for n = 1 or 2 over an oxygen partial pressure range of 103 to 105 Pa increased as the pressure decreased.

Excitation and Relaxation Processes of Impact Excitation Emission of Er3+ Ions in InP

ABSTRACTTime-resolved excitation and relaxation processes of the impact excitation emission (EL) at 1.54μm of Er3+ ions doped in InP were investigated in the temperature range from 77K to 330K. The decay process was almost exponential in all the measured temperature range and showed little thermal quenching. The decay time of 2ms at 77K decreased only to tms at 330K. This result contrasted with the large thermal quenching and nonexponential characteristics of the photoluminescence (PL) time decay at higher temperatures, suggesting different Er3+ centers excited between EL and PL. A two-emission-center model is proposed and the different behaviors of thermal quenching and time decay between EL and PL emissions are consistently explained.