Introducing structural defects such as vacancies, nanoprecipitates, and dislocations is a proven means of reducing lattice thermal conductivity. However, these defects tend to be detrimental to carrier mobility. Consequently, the overall effects for enhancing ZT are often compromised. Indeed, developing strategies allowing for strong phonon scattering and high carrier mobility at the same time is a prime task in thermoelectrics. Here we present a high-performance thermoelectric system of Pb(Sb□)SeTe (□ = vacancy; y = 0-0.4) embedded with unique defect architecture. Given the mean free paths of phonons and electrons, we rationally integrate multiple defects that involve point defects, vacancy-driven dense dislocations, and Te-induced nanoprecipitates with different sizes and mass fluctuations. They collectively scatter thermal phonons in a wide range of frequencies to give lattice thermal conductivity of ∼0.4 W m K, which approaches to the amorphous limit. Remarkably, Te alloying increases a density of nanoprecipitates that affect mobility negligibly and impede phonons significantly, and it also decreases a density of dislocations that scatter both electrons and phonons heavily. As y is increased to 0.4, electron mobility is enhanced and lattice thermal conductivity is decreased simultaneously. As a result, Pb(Sb□)SeTe exhibits the highest ZT ∼ 1.5 at 823 K, which is attributed to the markedly enhanced power factor and reduced lattice thermal conductivity, in comparison with a ZT ∼ 0.9 for Pb(Sb□)Se that contains heavy dislocations only. These results highlight the potential of defect engineering to modulate electrical and thermal transport properties independently. We also reveal the defect formation mechanisms for dislocations and nanoprecipitates embedded in Pb(Sb□)SeTe by atomic resolution spherical aberration-corrected scanning transmission electron microscopy.

SnSe emerges as a new class of thermoelectric materials since the recent discovery of an ultrahigh thermoelectric figure of merit in its single crystals. Achieving such performance in the polycrystalline counterpart is still challenging and requires fundamental understandings of its electrical and thermal transport properties as well as structural chemistry. Here we demonstrate a new strategy of improving conversion efficiency of bulk polycrystalline SnSe thermoelectrics. We show that PbSe alloying decreases the transition temperature between Pnma and Cmcm phases and thereby can serve as a means of controlling its onset temperature. Along with 1% Na doping, delicate control of the alloying fraction markedly enhances electrical conductivity by earlier initiation of bipolar conduction while reducing lattice thermal conductivity by alloy and point defect scattering simultaneously. As a result, a remarkably high peak ZT of ∼1.2 at 773 K as well as average ZT of ∼0.5 from RT to 773 K is achieved for Na(SnPb)Se. Surprisingly, spherical-aberration corrected scanning transmission electron microscopic studies reveal that NaSnPbSe (0 < x ≤ 0.2; y = 0, 0.01) alloys spontaneously form nanoscale particles with a typical size of ∼5-10 nm embedded inside the bulk matrix, rather than solid solutions as previously believed. This unexpected feature results in further reduction in their lattice thermal conductivity.

Thermoelectrics directly converts waste heat into electricity and is considered a promising means of sustainable energy generation. While most of the recent advances in the enhancement of the thermoelectric figure of merit (ZT) resulted from a decrease in lattice thermal conductivity by nanostructuring, there have been very few attempts to enhance electrical transport properties, i.e., the power factor. Here we use nanochemistry to stabilize bulk bismuth telluride (BiTe) that violates phase equilibrium, namely, phase-pure n-type KBiTe. Incorporated potassium and tellurium in BiTe far exceed their solubility limit, inducing simultaneous increase in the electrical conductivity and the Seebeck coefficient along with decrease in the thermal conductivity. Consequently, a high power factor of ∼43 μW cm K and a high ZT > 1.1 at 323 K are achieved. Our current synthetic method can be used to produce a new family of materials with novel physical and chemical characteristics for various applications.

Most reported thermoelectric modules suffer from considerable power loss due to high electrical and thermal resistivity arising at the interface between thermoelectric legs and metallic contacts. Despite increasing complaints on this critical problem, it has been scarcely tackled. Here we report the metallization layer of Fe−Ni alloy seamlessly securing skutterudite materials and metallic electrodes, allowing for a minimal loss of energy transferred from the former. It is applied to an 8couple thermoelectric module that consists of n-type (Mm,Sm) y Co 4 Sb 12 (ZT max = 0.9) and p-type DD y Fe 3 CoSb 12 (ZT max = 0.7) skutterudite materials. It performs as a diffusion barrier suppressing chemical reactions to produce a secondary phase at the interface. Consequent high thermal stability of the module results in the lowest reported electrical contact resistivity of 2.2−2.5 μΩ cm 2 and one of the highest thermoelectric power density of 2.1 W cm −2 for a temperature difference of 570 K. Employing a scanning transmission electron microscope equipped with an energy-dispersive X-ray spectroscope detector, we confirmed that it is negligible for atomic diffusion across the interface and resulting formation of a detrimental secondary phase to energy transfer and thermal stability of the thermoelectric module.

The thermoelectric (TE) community has mainly focused on improving the figure of merit (ZT) of materials. However, the output power of TE devices directly depends on the power factor (PF) rather than ZT. Effective strategies of enhancing PF have been elusive for Bi2Te3-based compounds, which are efficient thermoelectrics operating near ambient temperature. Here, we report ultrahigh carrier mobility of ∼467 cm2 V–1 s–1 and power factor of ∼45 μW cm–1 K–2 in a new n-type Bi2Te3 system with nominal composition Cu x Bi2Te3.17 (x = 0.02, 0.04, and 0.06). It is obtained by reacting Bi2Te3 with surplus Cu and Te and subsequently pressing powder products by spark plasma sintering (SPS). The SPS discharges excess Te but stabilizes the high extent of Cu in the structure, giving unique SPS Cu x Bi2Te3.17 samples. The analyzed composition is close to “Cu x Bi2Te3”. Their charge transport properties are highly unusual. Hall carrier concentration and mobility simultaneously increase with the higher mole fraction of Cu contrary to the typical carrier scattering mechanism. As a consequence, the electrical conductivity is considerably enhanced with Cu incorporation. The Seebeck coefficient is nearly unchanged by the increasing Cu content in contrast to the general understanding of inverse relationship between electrical conductivity and Seebeck coefficient. These effects synergistically lead to a record high power factor among all polycrystalline n-type Bi2Te3-based materials.

Despite extensive studies on emerging thermoelectric material SnSe, its n-type form is largely underdeveloped mainly due to the difficulty in stabilizing the carrier concentration at the optimal level. Here, we dually introduce Cl and PbSe to induce n-type conduction in intrinsic p-type SnSe. PbSe alloying enhances the power factor and suppresses lattice thermal conductivity at the same time, giving a highest thermoelectric figure of merit ZT of 1.2 at 823 K for n-type polycrystalline SnSe materials. The best composition is Sn 0.90 Pb 0.15 Se 0.95 Cl 0.05 . Samples prepared by the solid-state reaction show a high maximum ZT (ZT max ) ∼1.1 and ∼0.8 parallel and perpendicular to the press direction of spark plasma sintering, respectively. Remarkably, post-ball milling and annealing processes considerably reduce structural anisotropy, thereby leading to a ZT max ∼1.2 along both the directions. Hence, the direction giving a ZT max is controllable for this system using the specialized preparation methods for specimens. Spherical aberration-corrected scanning transmission electron microscopic analyses reveal the presence of heavily dense edge dislocations and strain fields, not observed in the p-type counterparts, which contribute to decreasing lattice thermal conductivity. Our theoretical calculations employing a Callaway−Debye model support the experimental results for thermal transport and microscopic structures.

The aim of this study was to investigate comorbidities in patients with end-stage renal disease, and to compare health-related quality of life (HRQOL) according to the type, and number of comorbidities. Methods: A total of 250 adults undergoing hemodialysis were recruited at local clinics. HRQOL was measured using the 12-item Medical Outcomes Study Short Form questionnaire. Data were analyzed using descriptive statistics, analysis of variance, and t test. Results: Around 70.8% of patients with end stage renal disease had 1 or more comorbidities, and the most common comorbidities were hypertension, diabetes, and cardiovascular disease. HRQOL was significantly different based on the number of comorbidities (F = 9.83, p < 0.001). The effect of comorbidities on the scores for mental health domains of the HRQOL questionnaire was not conclusive compared with the scores for the physical domain which were conclusive. Among the comorbidities, diabetes was associated with a lower quality of life. Conclusion: The customized management of diabetic and hypertensive patients is necessary for the early detection and prevention of chronic kidney disease, and slowing the progression of renal disease and managing cardiovascular risk factors is essential.

ObjectivesTo design a cloud computing-based Healthcare Software-as-a-Service (SaaS) Platform (HSP) for delivering healthcare information services with low cost, high clinical value, and high usability.MethodsWe analyzed the architecture requirements of an HSP, including the interface, business services, cloud SaaS, quality attributes, privacy and security, and multi-lingual capacity. For cloud-based SaaS services, we focused on Clinical Decision Service (CDS) content services, basic functional services, and mobile services. Microsoft's Azure cloud computing for Infrastructure-as-a-Service (IaaS) and Platform-as-a-Service (PaaS) was used.ResultsThe functional and software views of an HSP were designed in a layered architecture. External systems can be interfaced with the HSP using SOAP and REST/JSON. The multi-tenancy model of the HSP was designed as a shared database, with a separate schema for each tenant through a single application, although healthcare data can be physically located on a cloud or in a hospital, depending on regulations. The CDS services were categorized into rule-based services for medications, alert registration services, and knowledge services.ConclusionsWe expect that cloud-based HSPs will allow small and mid-sized hospitals, in addition to large-sized hospitals, to adopt information infrastructures and health information technology with low system operation and maintenance costs.