Accurate Excitation Energies of Point Defects from Fast Particle-Particle Random Phase Approximation Calculations.

We present an efficient particle-particle random phase approximation (ppRPA) approach that predicts accurate excitation energies of point defects, including the nitrogen-vacancy (NV-) and silicon-vacancy (SiV0) centers in diamond and the divacancy center (VV0) in 4H silicon carbide, with errors of ±0.2 eV compared with experimental values. Starting from the (N + 2)-electron ground state calculated with density functional theory (DFT), the ppRPA excitation energies of the N-electron system are calculated as the differences between the two-electron removal energies of the (N + 2)-electron system. We demonstrate that the ppRPA excitation energies converge rapidly with a few hundred canonical active-space orbitals. We also show that active-space ppRPA has weak DFT starting-point dependence and is significantly cheaper than the corresponding ground-state DFT calculation. This work establishes ppRPA as an accurate and low-cost tool for investigating excited-state properties of point defects and opens up new opportunities for applications of ppRPA to periodic bulk materials.

Highly stabilized and efficient thermoelectric copper selenide.

The liquid-like feature of thermoelectric superionic conductors is a double-edged sword: the long-range migration of ions hinders the phonon transport, but their directional segregation greatly impairs the service stability. We report the synergetic enhancement in figure of merit (ZT) and stability in Cu1.99Se-based superionic conductors enabled by ion confinement effects. Guided by density functional theory and nudged elastic band simulations, we elevated the activation energy to restrict ion migrations through a cation-anion co-doping strategy. We reduced the carrier concentration without sacrificing the low thermal conductivity, obtaining a ZT of ∼3.0 at 1,050 K. Notably, the fabricated device module maintained a high conversion efficiency of up to ∼13.4% for a temperature difference of 518 K without obvious degradation after 120 cycles. Our work could be generalized to develop electrically and thermally robust functional materials with ionic migration characteristics.

An AI-empowered indoor digital contact tracing system for COVID-19 outbreaks in residential care homes.

An AI-empowered indoor digital contact-tracing system was developed using a centralized architecture and advanced low-energy Bluetooth technologies for indoor positioning, with careful preservation of privacy and data security. We analyzed the contact pattern data from two RCHs and investigated a COVID-19 outbreak in one study site. To evaluate the effectiveness of the system in containing outbreaks with minimal contacts under quarantine, a simulation study was conducted to compare the impact of different quarantine strategies on outbreak containment within RCHs. The significant difference in contact hours between weekdays and weekends was observed for some pairs of RCH residents and staff during the two-week data collection period. No significant difference between secondary cases and uninfected contacts was observed in a COVID-19 outbreak in terms of their demographics and contact patterns. Simulation results based on the collected contact data indicated that a threshold of accumulative contact hours one or two days prior to diagnosis of the index case could dramatically increase the efficiency of outbreak containment within RCHs by targeted isolation of the close contacts. This study demonstrated the feasibility and efficiency of employing an AI-empowered system in indoor digital contact tracing of outbreaks in RCHs in the post-pandemic era.

Ionic Conductive Cellulose-Based Hydrogels with Superior Long-Lasting Moisture and Antifreezing Features for Flexible Strain Sensor Applications.

Nowadays, wearable devices derived from flexible conductive hydrogels have attracted enormous attention. Nevertheless, the utilization of conductive hydrogels in practical applications under extreme conditions remains a significant challenge. Herein, a series of inorganic salt-ion-enhanced conductive hydrogels (HPE-LiCl) consisting of hydroxyethyl cellulose, hydroxyethyl acrylate, lithium chloride, and ethylene glycol/water binary solvent were fabricated via a facile one-pot method. Apart from outstanding self-adhesion, high stretchability, and remarkable fatigue resistance, the HPE-LiCl hydrogels possessed especially excellent antifreezing and long-lasting moisture performances, which could maintain satisfactory flexibility and electric conductivity over extended periods of time, even in challenging conditions such as extremely low temperatures (as low as -40 °C) and high temperatures (as high as 80 °C). Consequently, the HPE-LiCl-based sensor could timely and accurately monitor various human motion signals even in adverse environments and after long-term storage. Hence, this work presents a facile strategy for the design of long-term reliable hydrogels as smart strain sensors, especially used in extreme environments.

Genomic Analysis Reveals Candidate Genes Underlying Sex-Linked Eyelid Coloboma, Feather Color Traits, and Climatic Adaptation in Huoyan Geese.

Driven by natural and artificial selection, the domestic Huoyan geese from Northern China have gradually generated specific phenotypes and climatic adaptations. To understand the genetic basis of the two specific phenotypes that are sex linked, including upper eyelid coloboma and gosling feather color, as well as the climatic adaptations of the Huoyan goose, which can contribute to the artificial selection and breeding of geese. We selected Huoyan geese and nine Southern Chinese goose breeds and identified their divergence on the genomic level. Using selective sweep analysis, we found that PTPRM on chromosome Z influences the upper eyelid coloboma phenotype of the Huoyan goose, and TYRP1 is a plausible candidate gene for the Huoyan gosling feather color. We obtained a number of genes related to cold adaptation in Huoyan geese, mainly involved in physiological functions such as metabolism, angiogenesis contraction and circulatory system, apoptosis, immunity, stress, and neural system. The most interesting candidates for cold adaptation are PIP5K1B and NMNAT3 that are associated with energy metabolism and stress. We also obtained some genes related to heat adaptation, including AGTPBP1, associated with neurology; GDA, associated with skin pigmentation; and NAA35, associated with apoptosis. These findings deepen our understanding of the genetics of specific phenotypes and climate adaptation in local geese and provide insights for the selection of goose breeds.

Wide-temperature-range thermoelectric n-type Mg3(Sb,Bi)2 with high average and peak zT values.

Mg3(Sb,Bi)2 is a promising thermoelectric material suited for electronic cooling, but there is still room to optimize its low-temperature performance. This work realizes >200% enhancement in room-temperature zT by incorporating metallic inclusions (Nb or Ta) into the Mg3(Sb,Bi)2-based matrix. The electrical conductivity is boosted in the range of 300-450 K, whereas the corresponding Seebeck coefficients remain unchanged, leading to an exceptionally high room-temperature power factor >30 µW cm-1 K-2; such an unusual effect originates mainly from the modified interfacial barriers. The reduced interfacial barriers are conducive to carrier transport at low and high temperatures. Furthermore, benefiting from the reduced lattice thermal conductivity, a record-high average zT > 1.5 and a maximum zT of 2.04 at 798 K are achieved, resulting in a high thermoelectric conversion efficiency of 15%. This work demonstrates an efficient nanocomposite strategy to enhance the wide-temperature-range thermoelectric performance of n-type Mg3(Sb,Bi)2, broadening their potential for practical applications.

Fe-pillared montmorillonite functionalized chitosan/gelatin foams for efficient removal of organic pollutants by integration of adsorption and Fenton degradation.

A Fe-pillared montmorillonite (Fe-MMT) functionalized bio-based foam (Fe-MMT@CS/G) was developed by using chitosan (CS) and gelatin (G) as the matrix for high-efficiency elimination of organic pollutants through the integration of adsorption and Fenton degradation. The results showed that the mechanical properties of as-obtained foam were strengthened by the addition of certain amounts of Fe-MMT. Interestingly, Fe-MMT@CS/G displayed efficient adsorption ability for charged pollutants under a wide range of pH. The adsorption processes of methyl blue (MB), methylene blue (MEB) and tetracycline hydrochloride (TCH) on Fe-MMT@CS/G were well described by the Freundlich isotherm model and pseudo-second-order kinetic model. The maximum adsorption capacities were 2208.24 mg/g for MB, 1167.52 mg/g for MEB, and 806.31 mg/g for TCH. Electrostatic interactions, hydrogen bonding and van der Waals forces probably involved the adsorption process. As expected, this foam could exhibit better removal properties toward both charged and uncharged organic pollutants through the addition of H2O2 to trigger the Fenton degradation reaction. For non-adsorbable and uncharged bisphenol A (BPA), the removal efficiency was dramatically increased from 1.20 % to 92.77 % after Fenton degradation. Additionally, it presented outstanding recyclability. These results suggest that Fe-MMT@CS/G foam is a sustainable and efficient green material for the alleviation of water pollution.

Linear Scaling Calculations of Excitation Energies with Active-Space Particle-Particle Random-Phase Approximation.

We developed an efficient active-space particle-particle random-phase approximation (ppRPA) approach to calculate accurate charge-neutral excitation energies of molecular systems. The active-space ppRPA approach constrains both indexes in particle and hole pairs in the ppRPA matrix, which only selects frontier orbitals with dominant contributions to low-lying excitation energies. It employs the truncation in both orbital indexes in the particle-particle and the hole-hole spaces. The resulting matrix, whose eigenvalues are excitation energies, has a dimension that is independent of the size of the systems. The computational effort for the excitation energy calculation, therefore, scales linearly with system size and is negligible compared with the ground-state calculation of the (N - 2)-electron system, where N is the electron number of the molecule. With the active space consisting of 30 occupied and 30 virtual orbitals, the active-space ppRPA approach predicts the excitation energies of valence, charge-transfer, Rydberg, double, and diradical excitations with the mean absolute errors (MAEs) smaller than 0.03 eV compared with the full-space ppRPA results. As a side product, we also applied the active-space ppRPA approach in the renormalized singles (RS) T-matrix approach. Combining the non-interacting pair approximation that approximates the contribution to the self-energy outside the active space, the active-space GRSTRS@PBE approach predicts accurate absolute and relative core-level binding energies with the MAEs around 1.58 and 0.3 eV, respectively. The developed linear scaling calculation of excitation energies is promising for applications to large and complex systems.

Performance of Rubber Concrete Containing Polypropylene and Basalt Fibers under Coupled Sulfate Attack and Freeze-Thaw Conditions: An Experimental Evaluation.

Rubber concrete (RC) is a new type of concrete that is currently receiving a lot of attention, solving serious pollution problems by grinding waste tires into granules and adding them to concrete. However, rubber concrete has deficiencies in mechanics and durability, and has been reinforced by adding fibers in many studies. In this study, the mechanical and durability properties of rubber concrete with added polypropylene and basalt fibers (PBRC) were investigated in a series of experiments including apparent morphology, mass, static compressive and tensile tests, ultrasonic non-destructive testing, and scanning electron microscope (SEM) tests under coupled environments of sulfate attack and freeze-thaw. The results showed that the mass loss rate of RC and PBRC gradually increased with the number of freeze-thaw cycles, with more pits and cement paste peeling from the specimen surface. Moreover, the compressive and splitting tensile strengths of RC and PBRC groups exhibited distinct trends, with the former group showing a lower residual strength relative to the latter. The residual compressive strength of the RC group was only 69.4% after 160 freeze-thaw cycles in 5% MgSO4 solution. However, it is worth noting that the addition of too many fibers also had a negative effect on the strength of the rubber concrete. Additionally, the scanning electron microscopy (SEM) results indicated that the fibers restricted the formation of microcracks in the microstructure and curtailed the brittleness of the concrete. This study can provide a valuable reference for the application of environmentally friendly material fibers in recycled aggregate concrete.

Origins, timing and introgression of domestic geese revealed by whole genome data.

BACKGROUND: Geese are among the most important poultry species in the world. The current generally accepted hypothesis is that the European domestic geese originated from greylag geese (Anser anser), and Chinese domestic geese have two origins, most of which originated from swan geese (Anser cygnoides), and the Yili goose originated from greylag geese. To explain the origin and demographic history of geese, we selected 14 goose breeds from Europe and China and wild populations of swan and greylag geese, and whole genome sequencing data were obtained for 74 samples. RESULTS: Population structure analysis and phylogenetic trees showed that the wild ancestor of Chinese domestic geese, except for Yili, is the swan geese, and the wild ancestor of Chinese Yili and European domestic geese is greylag geese. Analysis of the demographic history suggests that the domestication of Chinese geese occurred ~ 3499 years ago and that of the European geese occurred ~ 7552 years ago. Furthermore, gene flow was observed between domestic geese and their wild ancestors. Analysis of introgression showed that Yili geese had been introgressed by Chinese domestic geese, and the body size of Yili geese may be influenced by introgression events of some growth-related genes, including IGF-1. CONCLUSIONS: Our study provides evidence for the origin of geese at the genome-wide level and advances the understanding of the history of goose domestication and the traits affected by introgression events.

High Power Factor Nb-Doped TiO2 Thermoelectric Thick Films: Toward Atomic Scale Defect Engineering of Crystallographic Shear Structures.

Donor-doped TiO2-based materials are promising thermoelectrics (TEs) due to their low cost and high stability at elevated temperatures. Herein, high-performance Nb-doped TiO2 thick films are fabricated by facile and scalable screen-printing techniques. Enhanced TE performance has been achieved by forming high-density crystallographic shear (CS) structures. All films exhibit the same matrix rutile structure but contain different nano-sized defect structures. Typically, in films with low Nb content, high concentrations of oxygen-deficient {121} CS planes are formed, while in films with high Nb content, a high density of twin boundaries are found. Through the use of strongly reducing atmospheres, a novel Al-segregated {210} CS structure is formed in films with higher Nb content. By advanced aberration-corrected scanning transmission electron microscopy techniques, we reveal the nature of the {210} CS structure at the nano-scale. These CS structures contain abundant oxygen vacancies and are believed to enable energy-filtering effects, leading to simultaneous enhancement of both the electrical conductivity and Seebeck coefficients. The optimized films exhibit a maximum power factor of 4.3 × 10-4 W m-1 K-2 at 673 K, the highest value for TiO2-based TE films at elevated temperatures. Our modulation strategy based on microstructure modification provides a novel route for atomic-level defect engineering which should guide the development of other TE materials.

Evolution of defect structures leading to high ZT in GeTe-based thermoelectric materials.

GeTe is a promising mid-temperature thermoelectric compound but inevitably contains excessive Ge vacancies hindering its performance maximization. This work reveals that significant enhancement in the dimensionless figure of merit (ZT) could be realized by defect structure engineering from point defects to line and plane defects of Ge vacancies. The evolved defects including dislocations and nanodomains enhance phonon scattering to reduce lattice thermal conductivity in GeTe. The accumulation of cationic vacancies toward the formation of dislocations and planar defects weakens the scattering against electronic carriers, securing the carrier mobility and power factor. This synergistic effect on electronic and thermal transport properties remarkably increases the quality factor. As a result, a maximum ZT > 2.3 at 648 K and a record-high average ZT (300-798 K) were obtained for Bi0.07Ge0.90Te in lead-free GeTe-based compounds. This work demonstrates an important strategy for maximizing the thermoelectric performance of GeTe-based materials by engineering the defect structures, which could also be applied to other thermoelectric materials.

Numerical Study on Hydrodynamic Characteristics and Electrochemical Performance of Alkaline Water Electrolyzer by Micro-Nano Surface Electrode.

This study constructed a two-dimensional alkaline water electrolyzer model based on the two-phase flow Euler-Euler model. In the model, the micro-nano surface electrodes with different structure types and graphic parameters (distance, height, and width) were used and compared with the vertical flat electrode to evaluate their influence on electrolysis performance. The simulation results show that the performance of the micro-nano surface electrode is much better than that of the vertical flat electrode. The total length of micro-nano structural units relates to the contact area between the electrode and the electrolyte and affects the cell voltage, overpotential, and void fraction. When rectangular structural units with a distance, height, and width of 0.5 µm, 0.5 µm, and 1 µm are used, the total length of the corresponding micro-nano surface electrode is three times that of the vertical flat electrode, and the cathode overpotential decreases by 65.31% and the void fraction increases by 54.53% when it replaces the vertical flat electrode.

Describing Chemical Reactivity with Frontier Molecular Orbitalets.

Locality in physical space is critical in understanding chemical reactivity in the analysis of various phenomena and processes in chemistry, biology, and materials science, as exemplified in the concepts of reactive functional groups and active sites. Frontier molecular orbitals (FMOs) pinpoint the locality of chemical bonds that are chemically reactive because of the associated orbital energies and thus have achieved great success in describing chemical reactivity, mainly for small systems. For large systems, however, the delocalization nature of canonical molecular orbitals makes it difficult for FMOs to highlight the locality of the chemical reactivity. To obtain localized molecular orbitals that also reflect the frontier nature of the chemical processes, we develop the concept of frontier molecular orbitalets (FMOLs) for describing the reactivity of large systems. The concept of orbitalets was developed recently in the localized orbital scaling correction method, which aims for eliminating the delocalization error in common density functional approximations. Orbitalets are localized in both physical and energy spaces and thus contain both orbital locality and energy information. The FMOLs are thus the orbitalets with energies highest among occupied orbitalets and lowest among unoccupied ones. The applications of FMOLs to hexadeca-1,3,5,7,9,11,13,15-octaene in its equilibrium geometry, inter- and intra-molecular charge-transfer systems, and two transition states of a bifurcating reaction demonstrate that FMOLs can connect quantum mechanical treatments of chemical systems and chemical reactivities by locating the reactive region of large chemical systems. Therefore, FMOLs extend the role of FMOs for small systems and describe the chemical reactivity of large systems with energy and locality insight, with potentially broad applications.

User characteristics and service satisfaction of car sharing systems: Evidence from Hangzhou, China.

Car sharing has become a new mode of transport during the past two decades in the world. Its rapid growth in China has attracted a wide range of users and posed some problems. The main focus is on service efficiency and user satisfaction. To explore possible service enhancement and management intervention, this study aims at capturing the user characteristics according to different user types and scrutinizing their satisfaction with station-based one-way car sharing service. The study firstly illustrates descriptive statistics of user profile. This is followed by a study of user satisfaction influenced by user rates on staffs, the efficiency of rental process, vehicle situation, the use of credit card and their familiarity towards rental station. Furthermore, by clustering users according to the total travel time and distance during one rent, two different types of users are identified and defined as User Group A (UGA) and User Group B (UGB). To examine how fully do users utilize the shared cars, ANOVA was conducted implying family car ownership, total travel distance and main travel purpose have strong impact on total rental time for UGB, while for UGA, travel purpose and age have strong impact. Finally, ordinal logistic regression was introduced to find that for UGB, "shopping" is the main travel purpose with longer rental time, whereas for UGA, "out for business", "shopping", "visit friends" or "pick up others" are the main travel purposes with longer total travel time. Based on the findings, advices for operators on how to improve service quality and suggestions for government management strategy are discussed, respectively.

LibSC: Library for Scaling Correction Methods in Density Functional Theory.

In recent years, a series of scaling correction (SC) methods have been developed in the Yang laboratory to reduce and eliminate the delocalization error, which is an intrinsic and systematic error existing in conventional density functional approximations (DFAs) within density functional theory (DFT). On the basis of extensive numerical results, the SC methods have been demonstrated to be capable of reducing the delocalization error effectively and producing accurate descriptions for many critical and challenging problems, including the fundamental gap, photoemission spectroscopy, charge transfer excitations, and polarizability. In the development of SC methods, the SC methods were mainly implemented in the QM4D package that was developed in the Yang laboratory for research development. The heavy dependency on the QM4D package hinders the SC methods from access by researchers for broad applications. In this work, we developed a reliable and efficient implementation, LibSC, for the global scaling correction (GSC) method and the localized orbital scaling correction (LOSC) method. LibSC will serve as a lightweight and open-source library that can be easily accessed by the quantum chemistry community. The implementation of LibSC is carefully modularized to provide the essential functionalities for conducting calculations of the SC methods. In addition, LibSC provides simple and consistent interfaces to support multiple popular programing languages, including C, C++, and Python. In addition to the development of the library, we also integrated LibSC with two popular and open-source quantum chemistry packages, the Psi4 package and the PySCF package, which provides immediate access for general users to perform calculations with SC methods.

Effects of Fly Ash and Hexadecyltrimethoxysilane on the Compressive Properties and Water Resistance of Magnesium Oxychloride Cement.

The application of magnesium oxychloride cement (MOC) is promising, but its poor water resistance seriously hinders its development and application. In this paper, we describe a new type of MOC with excellent water resistance, prepared using fly ash and hexadecyltrimethoxysilane (HDTMS). SEM, XRD, FTIR, TG/DSC, and other microscopic-scale studies were conducted to investigate the mechanism underlying the water-resistance enhancement of the new MOC. It was found that adding 20% fly ash and 3% HDTMS can strengthen the water resistance of MOC while retaining high mechanical properties. In particular, the residual coefficient remained at 0.91 after 7 days of immersion. This is because these two additives, when used together, can increase the content of the gelling 5-phase of MOC, as well as optimize the pore structure of MOC.

Regulatory effects of hawthorn polyphenols on hyperglycemic, inflammatory, insulin resistance responses, and alleviation of aortic injury in type 2 diabetic rats.

Hawthorn polyphenol extract (HPE) is beneficial for patients with type 2 diabetes (T2D). However, the mechanism underlying its beneficial effects remains unclear. We investigated the inhibitory effects and mechanisms of HPE on insulin resistance, inflammation, and aortic injury in T2D rats, using metformin (MF) as a positive control. High-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS/MS) was used to determine the primary polyphenols in HPE. Hematoxylin & Eosin (H&E) staining was used to evaluate pathological conditions of the skeletal muscle, liver, and aorta vessels in each group. The levels of serum and intestinal tissue oxidative stress, tumor necrosis factor α (TNF-α), and inflammatory interleukin-6 (IL-6) were also assessed. Western blotting was used to evaluate protein expression levels in the associated molecular pathway. Volatile organic compounds (VOCs) from colon contents were determined using headspace-gas chromatography-ion mobility chromatography. Our results showed that supplementation with 300 mg HPE/kg body weight over four weeks significantly improved total cholesterol (TC), total triglyceride (TG), insulin, and lipopolysaccharide (LPS) levels in diabetic rats (p < 0.01). The lesions of skeletal muscle, liver, and aorta in diabetic rats were significantly improved. HPE supplementation also significantly downregulated the inflammatory factors (IL-6, TNF-α, and MCP-1) in the liver of diabetic rats via the SIRT1/AMPK/NF-κB signaling pathway. Furthermore, HPE significantly reduced insulin resistance in T2D rats by upregulating the phosphorylation of glucose absorption protein (GLUT4) and insulin resistance-associated proteins, p-IRS1, p-AKT, and p-PI3K, in the rat liver (p < 0.01). The findings show that HPE could also alleviate aortic injury by activating SIRT1 and regulating the NF-κB and Wnt2/ß-catenin signaling pathways. Overall, the results of this study suggest that both HPE and MF have similar inhibitory effects on T2D in rats and that HPE could be used as a functional food component in the adjuvant treatment of T2D.

Hawthorn polyphenols reduce high glucose-induced inflammation and apoptosis in ARPE-19 cells by regulating miR-34a/SIRT1 to reduce acetylation.

Diabetic retinopathy is a major complication in patients with diabetes. Herein, we investigate how hawthorn polyphenol extract (HPE) affects high glucose-induced oxidation, inflammation, and apoptosis in ARPE-19 cells. HPLC-MS/MS was used to determine HPE content and composition. Reactive oxygen species (ROS) production was assessed using fluorescence microscopy, while glucose-induced gene and protein expressions were analyzed using real-time PCR and western blotting in cells transfected with miR-34a mimics. We found that treating cells with 10 µg/ml of HPE, 30 µM procyanidin B2, chlorogenic acid, epicatechin, or resveratrol (positive control) significantly reduced ROS production and decreased apoptosis and inflammation-related factors (p < .01). Moreover, the expression level of SIRT1 was increased, while that of acetylated NF-κB p65 and p53 proteins was decreased. These data suggest that HPE can inhibit oxidative damage, inflammation, and apoptosis through the AMPK/SIRT1/NF-κB pathway, and decrease miR-34a/SIRT1/p53 pathway activation in ARPE-19 cells, thereby demonstrating a potential use as a food additive to mitigate hyperglycemia-induced retinal damage. PRACTICAL APPLICATIONS: Hawthorn polyphenol extract (HPE) significantly reduced ROS levels, apoptosis, and the expression of inflammation-related factors in ARPE-19 cells. HPE also inhibited the AMPK/SIRT1/NF-κB and miR-34a/SIRT1/p53 pathways, which are involved in hyperglycemia-induced inflammation and apoptosis of ARPE-19 cells by regulating acetylation. Thus, HPE, as a potential food additive, may mitigate hyperglycemia-induced retinal damage.

Enhancing the Thermoelectric Performance of Calcium Cobaltite Ceramics by Tuning Composition and Processing.

Calcium cobaltite (Ca3Co4O9) is a promising p-type thermoelectric oxide material. Here, we present an approach to optimize the thermoelectric performance of Ca3Co4O9 by controlling the chemical composition and fabrication process. Ca3-xBixCo3.92O9+δ (0.1 ≤ x ≤ 0.3) and Ca2.7Bi0.3CoyO9+δ (3.92 ≤ y ≤ 4.0) ceramics were prepared by Spark Plasma Sintering (SPS). Stoichiometric mixtures of raw materials were combined and calcined at 1203 K for 12 h, followed by SPS at 1023 K for 5 min at 50 MPa. The samples were subsequently annealed at 1023 or 1203 K for 12 h in air. XRD and HRTEM analyses confirmed the formation of the cobaltite misfit phase with minor amounts of secondary phases; SEM-EDS showed the presence of Bi-rich and Co-rich secondary phases. After annealing at 1203 K, the secondary phases were significantly reduced. By controlling the cobalt deficiency and level of bismuth substitution, the electrical conductivity was enhanced without degrading Seebeck coefficients, promoting a high power factor of 0.34 mW m-1 K-2 at 823 K (parallel to the ab planes, //ab). Due to enhanced phonon scattering, the thermal conductivity was reduced by 20%. As a result, a highly competitive ZT(//ab) of 0.16 was achieved for Ca2.7Bi0.3Co3.92O9+δ ceramics at 823 K.