Design, synthesis, and characterization of complex chalcogenides for energy storage and energy conversion applications

Srikanth Balijapelly, Missouri University of Science and Technology

Abstract

Through this investigation, complex chalcogenides with the combination of main group metals, transition metals, and rare earth metals have been synthesized using the building block approach and their structure-property relationships are evaluated. The main emphasis of research is on rationally designing new materials for applications in sodium and lithium ion conducting solid electrolytes, cathodes, thermoelectrics, and nonlinear optics. Along with the experimental studies, theoretical calculations are also employed to better understand the physicochemical properties of the synthesized compounds. The first part of the research will discuss designing alkali ion containing complex chalcogenides using the building block approach. This investigation resulted in the discovery of several new compounds with unique crystal structures and fascinating physicochemical properties namely, facile sodium ion diffusion with ionic conductivities reaching up to 0.12 mS/cm in interpenetrated structure Na3ZnGaQ4 (Q = S, Se), metamagnetic behavior in LiMnPS4, promising harmonic signals with high laser-induced damage threshold in Na8Mn2(Ge2Se6)2. The second part of the research will discuss the synthesis and characterization of complex chalcogenides for thermoelectric applications. In this study, interplay between composition and disorder in tuning thermoelectric properties is investigated in the makovickyite and pekoite-aikinite family of compounds. Through this investigation ultra-low thermal conductivities (<0.7 W/m.K) are achieved, which in combination with high Seebeck coefficients led to moderate zT values (0.1 – 0.2).