Abstract: Ag1-xPbmSbTe2+m (m = 6, 10, 18; x = 0, 0.5, 0.75) compounds were prepared by melting-spark
plasma sintering (SPS) process. The effects of m and x on the thermoelectric properties of the compounds
were investigated. The results indicate that all samples are n-type conduction. For Ag1-xPb18SbTe20 (x = 0,
0.5, 0.75), the electrical conductivity decreases, whereas Seebeck coefficient increases, with increasing
Ag concentration. For AgPbmSbTe2+m (m = 6, 10, 18), as m increases, the Seebeck coefficient slightly
decreases and the electrical conductivity increases first, with a maximum at m =10, and then decreases.
The thermal conductivity increases with increasing m.
Abstract: Polycrystalline AgPb18+xSbTe20 compounds with different Pb contents (x=1-4) were prepared
by melting method and spark plasma sintering techniques. The crystal structure and chemical composition
were determined by XRD and EPMA. The thermal conductivity, electrical conductivity and Seebeck
coefficient were measured in the temperature range of 300-800K. The dimensionless thermoelectric
figure of merit (ZT) of AgPb18+xSbTe20 (x=1-4) increases in the whole temperature range of 300-750K
which is different to the pure lead telluride compound. The maximum ZT value reaches 1.03 at 800K.
Abstract: Lead tin telluride based alloys are known p-type materials for thermoelectric applications,
in the 50-600oC temperature range. These alloys combine desired features of mechanical and
thermoelectric properties. The electronic transport properties of PbTe and Pb1-xSnxTe materials may
be strongly dependent on the preparation technique. Powder metallurgy process is known to introduce
defects and strains, that may alter carrier concentration. Under such non-equilibrium conditions the
thermoelectric properties are instable at the operating temperature. An appropriate annealing
treatment can eliminate this effect.. The present communication describes the annealing treatment
applied to cold compacted and sintered Pb1-xSnxTe materials.
Abstract: Polycrystalline samples of Bi2Te3 based alloys were prepared by powder metallurgy processing
including a melting-grinding and a sintering procedure of compacted pellets. Two sintering procedures as
hot-pressing and spark plasma sintering (SPS) were employed. The thermoelectric properties and
mechanical strength were measured in all case. Thermoelectric properties for p-type (Bi0.25Sb0.75)2Te3 and
n-type Bi2(Te0.2Se0.8)3 changed with sintering temperature in both sintering methods. Mechanical strength
and relative density increase with sintering temperature in two sintering procedures. The results firmly
suggest that both sintering procedures are promising to obtain high performance thermoelectric materials.
Abstract: Thermoelectric Ag-Bi-Sb-Te alloys with the general formula AgxBi0.5Sb1.5-xTe3 (x =0.05∼0.4)
were prepared by spark plasma sintering and their electrical properties were examined. The alloys exhibit
large electrical conductivities in the whole temperature range, which are approximate 11.0 and 3.5 times
those of pseudo-binary Bi0.5Sb1.5Te3 alloy at room temperature and 558K, respectively. The highest
power factor value of 1.80×10-3 (W.K-2.m-1) is obtained for the material (x = 0.1) at the temperature of
412K, being about 2.4 times that of pseudo-binary alloy Bi0.5Sb1.5Te3 at the corresponding temperature.
Abstract: Bi porous films were prepared via a simple process which involves solvothermal or thermal
treatment of Bi(NO3)3 and alumina membranes. The reducing reagent is helpful for the growth of Bi in the
channels of alumina templates. However, Bi networked X-shape nanowires would form when the
reaction was carried out under vacuum system. This method has been successfully applied to the synthesis
of other porous metal film. The pressure, reducing reagent and starting materials play a key role in the
growth of Bi films. A possible formation mechanism of Bi films and nanowires is proposed.
Abstract: PbTe based semiconductors are characterized by a narrow energy gap and can be used for IR
detectors, light emission diodes, lasers and thermoelectric devices. The objective of the present work was
to study the effect of oxidation on the properties of n- and p-type PbTe samples prepared by powder
metallurgy (bulk materials) and physical vapor deposition (thin films with thickness ∼1 μm). The samples
were characterized by SEM, AES and XRD. The Hall effect and electrical conductivity of PbTe samples
have been examined over the 80 – 300 K temperature range. The experimental results are accounted for in
the framework of a model that is based on: 1- the fast diffusion of oxygen along grain boundaries (GB); 2
- oxygen absorption that generates acceptor states at GB (short time annealing) and the growth of PbTe
oxides on GB with properties corresponding to wide band semiconductor (lengthy annealing); 3 - the
creation of potential barriers on GB due to oxidation with a thermally activated dependence of the
Abstract: The present communication is concerned with the interdiffusion kinetics and the interface
breakdown that take place in the Nb/NbC multilayer system as the result of thermal annealing in the
400-800oC temperature range. Within this temperature range carbon is the diffusing species. Carbon
diffuses from the carbide layer into the adjacent Nb layer, depleting its concentration within the carbide,
causing the nucleation and subsequent growth of an intermediate Nb2C layer and decreasing the width of
the original Nb layer. TEM examination of the cross-sections of the multilayer specimens provides data
regarding the evolution of the microstructure and, in particular, regarding the initial nucleation stage of
the newly formed Nb2C layer.
Abstract: The conversion efficiency of heat to electricity is the basic parameter of thermoelectric element,
thermoelectric unicouple and thermoelectric devices. In principle, the heat to electricity conversion
efficiency of thermoelectric element has been defined as the electrical output power of the element
divided by its thermal input power. Due to the heat loss by convection and radiation heat transfer the test
result of the heat to electricity conversion efficiency has a large errors. The authors present a test method
for heat to electricity conversion efficiency of thermoelectric unicouple. The thermal input power of
thermoelectric unicouple has been divided into the electrical output power plus thermal output power out
of the cold end of the unicouple. The later has been determined by a thermoelectric thermal power meter.
The method avoids the difficulties to measure the input thermal power into the hot side of the unicouple,
so that the convection and radiation heat lose out of the unicouple side can be ignored. Owing to Seebeck
Coefficient of the thermoelectric semiconductor materials could be many times of the metals, the
thermoelectric thermal power meter has high sensitivity, so that high test precision could be gained in test
for conversion efficiency of thermoelectric unicouple. The paper presents some test results for heat to
electricity conversion efficiency of thermoelectric unicouple, and discusses about the factors which affect
the test results.