74 research outputs found
Thermoelectric enhancement in PbTe with K, Na co-doping from tuning the interaction of the light and heavy hole valence bands
The effect of K and K-Na substitution for Pb atoms in the rock salt lattice
of PbTe was investigated to test a hypothesis for development of resonant
states in the valence band that may enhance the thermoelectric power. We
combined high temperature Hall-effect, electrical conductivity and thermal
conductivity measurements to show that K-Na co-doping do not form resonance
states but2 can control the energy difference of the maxima of the two primary
valence sub-bands in PbTe. This leads to an enhanced interband interaction with
rising temperature and a significant rise in the thermoelectric figure of merit
of p-type PbTe. The experimental data can be explained by a combination of a
single and two-band model for the valence band of PbTe depending on hole
density that varies in the range of 1-15 x 10^19 cm^-3.Comment: 8 figure
Band-Gap Nonlinearity in Lead Chalcogenide (PbQ, Q = Te, Se, S) Alloys
Narrow band-gap lead chalcogenides have been developed
for several optical and electronic applications. However, band-gap energies
of the ternary and quaternary alloys have received little attention compared
with the parent binary phases. Here, we have fabricated single-phase
ternary (PbTe)1−x(PbSe)x and quaternary (PbTe)0.9−y(PbSe)0.1(PbS)y and
(PbTe)0.65−z(PbSe)0.35(PbS)z alloys and shown that although lattice
parameters follow Vegard’s law as a function of composition, the bandgap
energies exhibit a substantial bowing effect. The ternary
(PbTe)1−x(PbSe)x system features a smaller bowing parameter predominantly
due to the difference in electronegativity between Se and Te,
whereas the larger bowing parameters in quaternary alloys are generated
from a larger crystal lattice mismatch and larger miscibility gap. These
findings can lead to further advances in tuning the band-gap and lattice
parameters for optical and electronic applications of lead chalcogenides
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