Tailoring local structural distortions and the associated ferroelectric instability in SnTe via Ge alloying resulted in ultralow lattice thermal conductivity which boosts zT to 1.6 at 721 K.
The key challenge for superior thermoelectric performance of SnTe is optimization of very high hole concentration (∼1021 cm−3) arising from inherent Sn vacancies. Partial control of charge carriers can be achieved by self-compensation via careful filling of the vacancies using excess Sn, although high thermal conductivity remained a concern. In this context, with deliberate doping, an anharmonicity in phonon dispersion can be generated to obtain a poor thermal conductivity. We report on point defects and soft phonon mode driven poor thermal conductivity in self-compensated Sn1.03Te with Mn doping. The obvious modification in the electronic band structure has been demonstrated by four times enhancement in thermopower for Sn0.93Mn0.1Te from Sn1.03Te, and metallic behavior of temperature dependent resistivity. The observed soft phonon mode and impurity localized mode in Raman spectra have been explained based on the created anharmonicity in Sn1.03Te crystal with Mn doping.
We demonstrate observation of Raman signals of different analytes adsorbed on carbonaceous materials, such as, chemically reduced graphene, graphene oxide (GO), multi-walled carbon nanotube (MWCNT), graphite and activated carbon. The analytes selected for the study were Rhodamine 6G (R6G) (in resonant conditions), Rhodamine B (RB), Nile blue (NBA), Crystal Violet (CV) and acetaminophen (paracetamol). All the analytes except paracetamol absorb and fluoresce in the visible region. In this article we provide experimental evidence of the fact that observation of Raman signals of analytes on such carbonaceous materials are more due to resonance effect, suppression of fluorescence and efficient adsorption and that this property in not unique to graphene or nanotubes but prevalent for various type of carbon materials.
An approach for utilizing magnetism to try to enhance thermoelectric properties of Mn doped self-compensated Sn1.03Te in context of its dilute magnetic nature.
ScN-rich (Sc,Nb) . Insertion of Nb into ScN thus yielded to a reduction in thermal conductivity by a factor 5 due to the mass contrast in ScN which increase the phonon scattering ion the material.3
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