Favorable Contact with Low Interfacial Resistance for n-Type TiCoSb-Based Thermoelectric Devices.

In the past decade, significant efforts have been made to develop efficient half-Heusler (HH) based thermoelectric (TE) materials. However, their practical applications remain limited due to various challenges occurring during the fabrication of TE devices, particularly the development of stable contacts with low interfacial resistance. In this study, we have made an effort to explore a stable contact material with low interfacial resistance for an n-type TiCoSb-based TE material, specifically TiNbCoSbBi as a proof of concept, using a straightforward facile synthesis route of spark plasma sintering.

Oxygen-Passivated Sulfur Vacancies in Monolayer MoS for Enhanced Piezoelectricity.

Modern-day applications demand onboard electricity generation that can be achieved using piezoelectric phenomena. Reducing the dimensionality of materials is a pathway to enhancing the piezoelectric properties. Transition-metal dichalcogenides have been shown to exhibit high piezoelectricity.

Realization of Band Convergence in p-Type TiCoSb Half-Heusler Alloys Significantly Enhances the Thermoelectric Performance.

Band engineering is a promising approach that proved successful in enhancing the thermoelectric performance of several families of thermoelectric materials. Here, we show how this mechanism can be induced in the p-type TiCoSbhalf-Heusler (HH) compound to effectively improve the Seebeck coefficient. Both the Pisarenko plot and electronic band structure calculations demonstrate that this enhancement is due to increased density-of-states effective mass resulting from the convergence of two valence band maxima.

In Situ Evolution of Secondary Metallic Phases in Off-Stoichiometric ZrNiSn for Enhanced Thermoelectric Performance.

The full-Heusler (FH) inclusions in the half-Heusler (HH) matrix is a well-studied approach to reduce the lattice thermal conductivity of ZrNiSn HH alloy. However, excess Ni in ZrNiSn may lead to the in situ formation of FH and/or HH alloys with interstitial Ni defects. The excess Ni develops intermediate electronic states in the band gap of ZrNiSn and also generates defects to scatter phonons, thus providing additional control to tailor electronic and phonon transport properties synergistically.

Compositional Tailoring for Realizing High Thermoelectric Performance in Hafnium-Free n-Type ZrNiSn Half-Heusler Alloys.

Compositional tailoring enables fine-tuning of thermoelectric (TE) transport parameters by synergistic modulation of electronic and vibrational properties. In the present work, the aspects of compositionally tailored defects have been explored in ZrNiSn-based half-Heusler (HH) TE materials to achieve high TE performance and cost effectiveness in n-type Hf-free HH alloys. In off-stoichiometric Ni-rich ZrNiSn alloys in a low Ni doping limit ( < 0.

Surface-Engineered Nanostructure-Based Efficient Nonpolar GaN Ultraviolet Photodetectors.

Surface-engineered nanostructured nonpolar (112̅0) gallium nitride (GaN)-based high-performance ultraviolet (UV) photodetectors (PDs) have been fabricated. The surface morphology of a nonpolar GaN film was modified from pyramidal shape to flat and trigonal nanorods displaying facets along different crystallographic planes. We report the ease of enhancing the photocurrent (5.

Enhancement in thermoelectric performance of SiGe nanoalloys dispersed with SiC nanoparticles.

SiGe is one of the most widely used thermoelectric materials for radioisotope thermoelectric generator applications for harnessing waste-heat at high temperatures. In the present study, we report a simple experimental strategy for enhancing the thermoelectric and mechanical properties of n-type SiGe nanoalloys by dispersing SiC nanoparticles in a SiGe nanoalloy matrix. This strategy yielded a high value of figure-of-merit (ZT) of ∼1.

An interaction potential to study the thermal structure evolution of a thermoelectric material: β-Cu Se.

An interaction potential model has been developed, for the first time, for β-Cu Se using the ab initio derived data. The structure and elastic constants of β-Cu Se using the derived force-field are within a few percent of DFT derived structure and elastic constants and reported experimental structure. The derived force-field also shows remarkable ability to reproduce temperature dependent behavior of the specific heat and thermal expansion coefficient.

Wet chemical etching induced stress relaxed nanostructures on polar & non-polar epitaxial GaN films.

We report formation of aligned nanostructures on epitaxially grown polar and nonpolar GaN films via wet chemical (hot HPO and KOH) etching. The morphological evolution exhibited stress relaxed faceted nanopyramids, flat/trigonal nanorods and porous structures with high hydrophilicity and reduced wettability. The nanostructured films divulged significant suppression of defects and displayed an enhanced intensity ratio of the near band edge emission to the defect band.

Emerging cool white light emission from Dy(3+) doped single phase alkaline earth niobate phosphors for indoor lighting applications.

Single-phase cool white-light emitting BaNb2O6:Dy(3+) phosphors have been synthesized via a conventional solid-state reaction method and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) observations and spectrofluorophotometric measurements. XRD and Rietveld structural refinement studies confirm that all the samples exhibit pure orthorhombic structure [space group -C2221(20)]. SEM observations reveal the dense particle packaging with irregular morphology in a micron range.

Luminescence and advanced mass spectroscopic characterization of sodium zinc orthophosphate phosphor for low-cost light-emitting diodes.

A new rare-earth-free NaZnPO4:Mn(2+) (NZP:Mn) phosphor powder has been developed by our group and investigated meticulously for the first time using secondary ion mass spectroscopy and chemical imaging techniques. The studies confirmed the effective incorporation of Mn(2+) into the host lattice, resulting in an enhancement of photoluminescence intensity. Phase purity has been verified and structure parameters have been determined successfully by Rietveld refinement studies.

The role of nanoscale defect features in enhancing the thermoelectric performance of p-type nanostructured SiGe alloys.

Despite SiGe being one of the most widely studied thermoelectric materials owing to its application in radioisotope thermoelectric generators (RTG), the thermoelectric figure-of merit (ZT) of p-type SiGe is still quite low, resulting in poor device efficiencies. In the present study, we report a substantial enhancement in ZT∼ 1.2 at 900 °C for p-type nanostructured Si80Ge20 alloys by creating several types of defect features within the Si80Ge20 nanostructured matrix in a spectrum of nano to meso-scale dimensions during its nanostructuring, by employing mechanical alloying followed by spark plasma sintering.

Bulk superconductivity in bismuth oxysulfide Bi4O4S3.

A very recent report on the observation of superconductivity in Bi(4)O(4)S(3) [Mizuguchi, Y.; http://arxiv.org/abs/1207.