Driven by a need to develop low-cost and thermally stable materials for thermoelectric applications, donor-substituted strontium titanate is considered as a promising alternative to traditional thermoelectrics. The complex defect chemistry of SrTiO3-based materials imposes various limitations on identifying the relevant effects exerted on the electronic band structure and heat transfer, being a subject of debate and intensive research. Based on combined XRD, SEM/EDS, HRTEM, XPS, and TGA studies and measurements of thermoelectric properties, this work uncovers the particular role of various structural defects in electrical and thermal transport in Sr1±yTi0.9Nb0.1O3±δ, selected as a model system. Introduction of A-site cation vacancies provides a synergistic effect of combining fast charge transport in the perovskite lattice and suppressing the thermal conductivity mostly due to simultaneous generation of oxygen vacancies. The presence of oxygen vacancies promotes more efficient phonon scattering compared to Ruddlesden–Popper-type layers. These findings provide a link between structural and thermoelectric properties, offering further prospects for seeking highly performing SrTiO3-based thermoelectrics by tailoring the defect chemistry mechanisms.
1 September 2013 in Journal of the European Ceramic Society
Interest in producing films from renewable and biodegradable polymers, such as polysaccharides, has increased in recent years with the aim of reducing the environmental pollution caused by petroleum-based plastics. Additionally, combining the thermoplastic property of starch with the antioxidant and antimicrobial activities of chitosan is of great interest to develop active materials for food packaging. This study aims the preparation of thermoplastic blended starch-chitosan films mechanically reinforced with reduced graphene oxide (rGO). Blending the starch with chitosan and rGO showed that films had a hydrophobic surface (>100°), low water solubility (weight loss less than 10%), and improved antioxidant activity. Furthermore, blended film prepared with 75% starch and 25% chitosan with rGO achieved the maximum value of electrical conductivity (6.51 × 10-3 S/m) while maintaining the heat sealing properties of starch. The functional properties and heat sealability of starch-chitosan blended films with rGO enhance their application for active food packaging.
1 April 2019 in Journal of the European Ceramic Society