CAS: Solution Routes Towards Metastable Functional Chalcogenides

Iowa State University, Ames IA

Investigators

Abstract

Non-technical Summary Chalcogenide materials, i.e. inorganic materials containing sulfur, selenium or tellurium, are widely used in various applications. Development of novel chalcogenide materials with improved magnetic and thermoelectric characteristics is crucial for the advances in renewable energy harvesting, energy conversion and storage, and information and data storage, among others. In this project, supported by the Solid State and Materials Chemistry program in NSF’s Division of Materials Research, Prof. Kovnir and his research group study approaches to enhancing the solvothermal synthetic capabilities by developing novel synthetic techniques, and the sustainable synthesis of chalcogenide functional materials. The new synthesis methods stabilize metastable functional materials with unprecedented composition, structural fragments, and properties which are not attainable by traditional high-temperature solid state syntheses. Additionally, the researchers prepare unique layered structures of hybrid materials, materials that contain more than one distinct material component. The large interlayer separation makes transition metal-chalcogen layers accessible for soft chemistry modification, stabilizing unprecedented metastable chalcogenides. As part of this award, educational efforts focus on communicating science and chemistry to the public and educating students in Prof. Kovnir’s group to be effective in such communication. Graduate and undergraduate students in Prof. Kovnir’s group are engaged in exciting yet educational chemistry demonstrations at local K-12 schools, and Des Moines Science Center to foster the interest of the general public in STEM. Technical Summary Current solvothermal synthesis is limited to a narrow temperature window dictated by slow kinetics of the reaction near room temperature, or container stability and reactivity at the high-temperature end. In this project, supported by the Solid State and Materials Chemistry program in NSF’s Division of Materials Research, two expansions for the capabilities of current solvothermal synthesis are the development of sustainable activated selenium precursor to perform reaction at near room temperature, and pressurized silica ampoules and molten salts for the high temperature range. A rational combination of the developed synthetic techniques allows for the synthesis of various chalcogenide materials, including chiral hybrid compounds and metastable doped and substituted all-inorganic chalcogenides. Systematic investigations of the reaction mechanisms and structure-property relationships for the produced compounds are carried out to reveal the factors controlling magnetic, thermoelectric, and superconducting properties in these compounds. The new approach produces metastable functional materials with unique properties. Educational efforts are focused on communicating science and chemistry to the public and also educating students to be effective in such communication, in addition to providing a comprehensive materials chemistry education for the students involved in the project. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.