Research Seminar Abstract
The discovery of functional complex oxides requires the development of new low-temperature syntheses that can selectively form a desired material. Low-temperature solid-state reactions provide conditions that allow for kinetic control of the reaction pathway, which can lead to the discovery of new materials, or synthesis of materials that lie away from thermodynamic equilibrium (metastability). Additionally, lower temperature reactions (<900ºC) provide conditions that allow for in situ characterization of reaction pathways. Analysis of these pathways leads to an understanding of the limiting steps in a formation of these materials, which promotes the discovery of new strategies in approaching solid-state synthetic chemistry.
Using solid-state metathesis reactions with the general composition of: AMO2 + REOX → REMO3 + AX (where A = alkali metal, M = transition metal, RE = rare-earth metal, X = halide), the synthesis of complex oxides occurs at low temperatures (500-900ºC). This presentation examines how phase behavior changes with composition of precursors in the preparation of yttrium manganese oxides and how precursor composition can be used to control the formation of different phases, including metastable Y2Mn2O7. Also, we show that the formation of complex oxides is pathway dependent, or dependent on the formation of specific intermediates. Finally, we illustrate that these metathesis reactions provide a general reaction scheme for targeting complex oxides.