Regulating Multiscale Defects to Enhance the Thermoelectric Performance of Ca0.87Ag0.1Dy0.03MnO3 Ceramics.

Achieving high thermoelectric properties of CaMnO3 ceramics is significant for its applications at high temperature. Herein, Ca0.87Ag0.1Dy0.03MnO3 ceramics with plate-like template seeds additives were prepared by using a solid-state reaction method. The multiscale defects, including grain boundaries, oxygen defects, and Ag nanoprecipitations, which were regulated by the different sintering atmospheres, were beneficial for electron transport and phonon scattering. The grain boundaries as coherent interfaces could act as an alternative phonon scattering source. Oxygen vacancies coupled with Ag nanoprecipitations were verified by geometric phase analysis and annular bright-field analysis. The decrement in oxygen vacancies concentration strongly depended on the enriched oxygen environment, which could reduce electrical resistivities. Compared to the sample sintered at Ar atmosphere, a 17.5 times increment in power factor and a 20.1% reduction of the total thermal conductivity were obtained for the sample sintered at O2 atmosphere. As a result, the maximum ZT value of 0.22 was obtained at 500 °C. It is an effective way for improving the thermoelectric performance of oxide-based thermoelectric materials.

Linear viscoelastic properties of the vertex model for epithelial tissues.

Epithelial tissues act as barriers and, therefore, must repair themselves, respond to environmental changes and grow without compromising their integrity. Consequently, they exhibit complex viscoelastic rheological behavior where constituent cells actively tune their mechanical properties to change the overall response of the tissue, e.g., from solid-like to fluid-like. Mesoscopic mechanical properties of epithelia are commonly modeled with the vertex model. While previous studies have predominantly focused on the rheological properties of the vertex model at long time scales, we systematically studied the full dynamic range by applying small oscillatory shear and bulk deformations in both solid-like and fluid-like phases for regular hexagonal and disordered cell configurations. We found that the shear and bulk responses in the fluid and solid phases can be described by standard spring-dashpot viscoelastic models. Furthermore, the solid-fluid transition can be tuned by applying pre-deformation to the system. Our study provides insights into the mechanisms by which epithelia can regulate their rich rheological behavior.