Synthesis and Characterization of Novel Polar Magnetic Compounds

Polar magnetic oxides (PMOs) have multiple applications in energy-conversion technologies including computer memory and biosensors. Currently, however, it is still very challenging to predict and design novel PMOs due to minimal design strategies. In this project, a novel synthesis method was developed to convert the centrosymmetric tetragonal crystal structure into a polar crystal structure. X-Ray Diffraction (XRD) results revealed the successful preparation of the polar phase in three different novel materials. Furthermore, the polar space group was confirmed through Transmission Electron Microscopy (TEM). Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS) results indicated the homogenous distribution of each atom. The results of this project are encouraging as this novel synthesis method can be used to explore yet-to-be-discovered materials.

Polar materials are inorganic solid-state materials with a polar axis but no inversion symmetry in the crystal structure. They exhibit unique physical properties including efficient transfer of electric charges. Similarly, metal oxides are significant as they can catalyze a variety of reactions that can be utilized in biosensor applications. For that reason, polar metallic oxides (PMOs) are extremely important in the development of computer memory, transducers, and many other areas related to energy-conversion technologies. Currently, however, it is still very challenging to predict and design novel PMOs due to minimal design strategies. Therefore, my question is: How can we synthesize novel PMOs more effectively and efficiently?

My mentor and I tackled this question by developing a novel synthesis method that converts the centrosymmetric tetragonal crystal structure into a polar crystal structure. The Ruddlesden-Popper compounds adopt the non-polar space group with face-sharing octahedra trimers connected by corner-sharing octahedra. In each trimer, the middle distorted octahedra are symmetrically connected to two identical distorted octahedra.

Our novel synthesis method alters non-polar chemical structure into a polar crystal structure by changing the composition of octahedra in the trimmer. As a result of the compositional change, each trimer will contain three different octahedra, which contributes to the development of the overall noncentrosymmetric tetragonal crystal structure.

X-Ray Diffraction (XRD) results revealed the successful preparation of the polar phase in three different novel materials. Furthermore, the polar space group was confirmed through Transmission Electron Microscopy (TEM). Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS) results indicated the homogenous distribution of each atom. Since our results show the successful preparation of polar crystalline phases, our novel synthesis method could possibly be used to explore yet-to-be-discovered materials.